Probability · Class 10 Mathematics: 117 MCQs with answers
All 117 multiple-choice questions from this kit, free and with no sign-up.
Warm-up · 32 questions
Q1. The classical definition of probability is
BeginnerShow answer & explanation
$\frac{\text{favourable}}{\text{total}}$
Wanted over total.
Q2. That definition requires the outcomes to be
BeginnerShow answer & explanation
equally likely
Otherwise no outcome may be counted the same as another.
Q3. An OUTCOME is
BeginnerShow answer & explanation
one possible result of the experiment
A single result.
Q4. An EVENT is
BeginnerShow answer & explanation
a collection of outcomes
Anything you might ask about.
Q5. The probability of an even number on one fair die is
BeginnerShow answer & explanation
$\frac12$
Three of the six faces.
Q6. Every probability satisfies
BeginnerShow answer & explanation
$0 \le P(E) \le 1$
A part cannot exceed the whole.
Q7. $P(E) = 0$ means the event is
BeginnerShow answer & explanation
impossible
No outcome is favourable.
Q8. $P(E) = 1$ means the event is
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certain
Every outcome is favourable.
Q9. The probability of rolling a 7 on one ordinary die is
BeginnerShow answer & explanation
0
No face shows 7.
Q10. The probability of rolling a number less than 7 on one die is
BeginnerShow answer & explanation
1
All six faces qualify.
Q11. The complementary event $\bar{E}$ is
BeginnerShow answer & explanation
the event that $E$ does not happen
Everything else.
Q12. The complement rule states that
BeginnerShow answer & explanation
$P(\bar{E}) = 1 - P(E)$
The event happens or it does not.
Q13. Assertion (A): The probability of an event can never exceed 1. Reason (R): A probability is written either as a fraction or as a decimal.
BeginnerShow answer & explanation
Both A and R are true, but R is not the correct explanation of A
Both are true, but how a probability is written does not bound it; the count of favourable outcomes does.
Q14. The answer $\frac{18}{36}$ should be written as
BeginnerShow answer & explanation
$\frac12$
Lowest terms.
Q15. The first step in any probability question should be to
BeginnerShow answer & explanation
list the outcomes
Almost every error is a counting error.
Q16. If $P(E) = 0.35$, then $P(\bar{E})$ is
BeginnerShow answer & explanation
0.65
$1 - 0.35$.
Q17. Which statement is true?
BeginnerShow answer & explanation
$P(E) + P(\bar{E}) = 1$
The event happens or it does not.
Q18. Probability as a subject began with
BeginnerShow answer & explanation
a question about dividing the stakes of an unfinished game
Two seventeenth-century gamblers.
Q19. State the classical definition of probability and the condition it requires.
BeginnerShow answer & explanation
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Q20. Distinguish an outcome from an event, with an example from a single die.
BeginnerShow answer & explanation
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Q21. The number of outcomes when $n$ coins are tossed is
BeginnerShow answer & explanation
$2^n$
Each coin doubles the count.
Q22. Three coins tossed together have how many outcomes?
BeginnerShow answer & explanation
eight
$2^3$.
Q23. Two dice have how many outcomes?
BeginnerShow answer & explanation
36
$6 \times 6$.
Q24. A DOUBLE on two dice means
BeginnerShow answer & explanation
both dice show the same number
(1,1) through (6,6).
Q25. A standard pack contains
BeginnerShow answer & explanation
52 cards in 4 suits of 13
Four thirteens.
Q26. The red suits are
BeginnerShow answer & explanation
hearts and diamonds
26 red cards in all.
Q27. How many red cards are in a pack?
BeginnerShow answer & explanation
26
Two suits of thirteen.
Q28. $P(\text{a heart})$ from a full pack is
BeginnerShow answer & explanation
$\frac14$
$\frac{13}{52}$.
Q29. $P(\text{a king})$ from a full pack is
BeginnerShow answer & explanation
$\frac{1}{13}$
$\frac{4}{52}$.
Q30. The first thing to write in any question of this topic is
BeginnerShow answer & explanation
the total number of outcomes
Adjusted for any removals.
Q31. A bag game needs a six to start. $P(\text{starting on the first throw})$ of one die is
BeginnerShow answer & explanation
$\frac16$
One favourable face of six.
Q32. Describe the structure of a pack of cards, including colours and face cards.
BeginnerShow answer & explanation
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Building up · 43 questions
Q33. A drawing pin tossed in the air illustrates
IntermediateShow answer & explanation
two outcomes that are NOT equally likely
Point-up and point-down do not happen equally often.
Q34. Tossing two coins has how many equally likely outcomes?
IntermediateShow answer & explanation
four
HH, HT, TH, TT.
Q35. An answer of $\frac76$ for a probability indicates
IntermediateShow answer & explanation
an arithmetic mistake
No probability can exceed 1.
Q36. If $P(E) = \frac{3}{8}$, then $P(\bar{E})$ is
IntermediateShow answer & explanation
$\frac58$
$1 - \frac38$.
Q37. The probability of drawing a king from a pack is $\frac{1}{13}$. The probability of not drawing one is
IntermediateShow answer & explanation
$\frac{12}{13}$
$1 - \frac{1}{13}$.
Q38. The complement is worth using when
IntermediateShow answer & explanation
the event is harder to count than its opposite
One short count instead of one long one.
Q39. Which word usually signals that the complement will be quicker?
IntermediateShow answer & explanation
'not'
Along with 'at least' and 'none'.
Q40. The probabilities of all the outcomes of an experiment add to
IntermediateShow answer & explanation
1
Something must happen.
Q41. Which of these is NOT an acceptable way to write a probability?
IntermediateShow answer & explanation
'1 : 6'
A ratio states odds, not a probability.
Q42. A bag has 5 red and 15 blue balls. The probability of drawing red is
IntermediateShow answer & explanation
$\frac14$
$\frac{5}{20}$, reduced.
Q43. For that same bag, the probability of not drawing red is
IntermediateShow answer & explanation
$\frac34$
$1 - \frac14$.
Q44. A weather forecast of '70% rain' expresses a probability of
IntermediateShow answer & explanation
$\frac{7}{10}$
A percentage is a fraction out of 100.
Q45. Assertion (A): Listing the outcomes before counting prevents most errors in this chapter. Reason (R): Tossing two coins has four outcomes, not three, which is only obvious once they are written out.
IntermediateShow answer & explanation
Both A and R are true, and R is the correct explanation of A
The listing makes HT and TH visibly different.
Q46. A bag has 3 white and 9 black balls. $P(\text{white})$ is
IntermediateShow answer & explanation
$\frac14$
$\frac{3}{12}$, reduced.
Q47. Explain why tossing two coins has four outcomes rather than three, and find the probability of exactly one head.
IntermediateShow answer & explanation
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Q48. Prove that every probability lies between 0 and 1, and say what the two extremes mean.
IntermediateShow answer & explanation
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Q49. Define the complementary event and derive the complement rule.
IntermediateShow answer & explanation
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Q50. A bag contains 5 red and 15 blue balls. Find the probability of drawing a red ball, and of not drawing one.
IntermediateShow answer & explanation
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Q51. State the conventions for writing a probability, and give one form that is not acceptable.
IntermediateShow answer & explanation
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Q52. With three coins, $P(\text{no heads})$ is
IntermediateShow answer & explanation
$\frac18$
Only TTT.
Q53. Are $(2,5)$ and $(5,2)$ the same outcome for two dice?
IntermediateShow answer & explanation
no, the dice are distinguishable
First die and second die are different positions.
Q54. How many ways can two dice total 7?
IntermediateShow answer & explanation
six
(1,6), (2,5), (3,4), (4,3), (5,2), (6,1).
Q55. $P(\text{total } 6)$ for two dice is
IntermediateShow answer & explanation
$\frac{5}{36}$
Five ways: (1,5), (2,4), (3,3), (4,2), (5,1).
Q56. $P(\text{total } 12)$ for two dice is
IntermediateShow answer & explanation
$\frac{1}{36}$
Only (6,6).
Q57. Which total is the most likely on two dice?
IntermediateShow answer & explanation
7
It can be made in six ways.
Q58. $P(\text{a double})$ on two dice is
IntermediateShow answer & explanation
$\frac16$
Six of the thirty-six outcomes.
Q59. The face cards are
IntermediateShow answer & explanation
the jack, queen and king
Three per suit.
Q60. How many face cards are in a pack?
IntermediateShow answer & explanation
12
Three per suit, four suits.
Q61. Assertion (A): An ace is a face card. Reason (R): The face cards of a pack are the jack, the queen and the king.
IntermediateShow answer & explanation
A is false but R is true
R is true and is exactly why A is false: the ace is not among them.
Q62. Assertion (A): Two dice give 36 equally likely outcomes. Reason (R): Each die has 6 faces and the two dice are distinguishable.
IntermediateShow answer & explanation
Both A and R are true, and R is the correct explanation of A
$6 \times 6$ ordered pairs, all equally likely.
Q63. $P(\text{a red king})$ is
IntermediateShow answer & explanation
$\frac{1}{26}$
Two cards out of 52.
Q64. $P(\text{a face card})$ is
IntermediateShow answer & explanation
$\frac{3}{13}$
$\frac{12}{52}$.
Q65. $P(\text{the queen of spades})$ is
IntermediateShow answer & explanation
$\frac{1}{52}$
Exactly one card.
Q66. All the face cards are removed from a pack. How many cards remain?
IntermediateShow answer & explanation
40
$52 - 12$.
Q67. When cards are removed before a draw, you must adjust
IntermediateShow answer & explanation
both the favourable count and the total
Using 52 afterwards is the commonest error here.
Q68. 'At least one head' when three coins are tossed means
IntermediateShow answer & explanation
one, two or three heads
One or more.
Q69. Two dice are thrown. $P(\text{the same number on both})$ is
IntermediateShow answer & explanation
$\frac16$
That is a double.
Q70. Two dice are thrown. $P(\text{a total of 1})$ is
IntermediateShow answer & explanation
0
The smallest possible total is 2.
Q71. Two coins are tossed. $P(\text{at least one tail})$ is
IntermediateShow answer & explanation
$\frac34$
$1 - P(HH) = 1 - \frac14$.
Q72. List the outcomes when three coins are tossed, and find the probability of exactly two heads.
IntermediateShow answer & explanation
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Q73. For the same three coins, find the probability of at least one head, and say why the complement is quicker.
IntermediateShow answer & explanation
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Q74. For two dice, find the probability of a total of 7, of 12, and of a double.
IntermediateShow answer & explanation
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Q75. Find the probability of drawing a heart, a king, a red king and a face card from a full pack.
IntermediateShow answer & explanation
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Topper level · 42 questions
Q76. The probability of exactly one head when two coins are tossed is
AdvancedShow answer & explanation
$\frac12$
HT and TH, so $\frac24$.
Q77. Calling that probability $\frac13$ is wrong because
AdvancedShow answer & explanation
'one of each' happens in two ways, not one
HT and TH are different outcomes.
Q78. Two dice are thrown. The probability that the total is 7 is
AdvancedShow answer & explanation
$\frac16$
Six of the thirty-six pairs total 7.
Q79. Assertion (A): An event with a very small probability is impossible. Reason (R): An event is impossible exactly when its probability is 0.
AdvancedShow answer & explanation
A is false but R is true
R is true and is why A is false: small is not zero.
Q80. Two dice are thrown. The probability of a total other than 7 is
AdvancedShow answer & explanation
$\frac56$
$1 - \frac16$, using the complement.
Q81. If a list of probabilities does not add to 1, then
AdvancedShow answer & explanation
one is wrong or an outcome was missed
It is a free check on the whole question.
Q82. 'At least one head' differs from 'exactly one head' because
AdvancedShow answer & explanation
'at least one' also includes two heads
Read the phrase before counting.
Q83. A box holds 20 bulbs, 4 of them defective. The probability that one chosen at random is good is
AdvancedShow answer & explanation
$\frac45$
$1 - \frac{4}{20} = 1 - \frac15$.
Q84. A fair die is rolled. $P(\text{a factor of } 6)$ is
AdvancedShow answer & explanation
$\frac23$
The factors of 6 among 1 to 6 are 1, 2, 3 and 6 — four faces.
Q85. A fair die is rolled. $P(\text{a prime number})$ is
AdvancedShow answer & explanation
$\frac12$
The primes among 1 to 6 are 2, 3 and 5.
Q86. Saying an experiment is 'random' means
AdvancedShow answer & explanation
every outcome is equally likely
It is a statement about balance, not about ignorance.
Q87. Assertion (A): A probability may be written as a ratio such as 1 : 6. Reason (R): A probability is a number between 0 and 1.
AdvancedShow answer & explanation
A is false but R is true
R is true and shows A false: a ratio is not such a number, and 1 : 6 is odds, not a probability.
Q88. Two dice are thrown. Find the probability that the total is not 7, and explain why the complement is the quicker route.
AdvancedShow answer & explanation
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Q89. Explain the difference between 'at least one head' and 'exactly one head' when two coins are tossed, and find both probabilities.
AdvancedShow answer & explanation
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Q90. Explain why an event with a very small probability is not the same as an impossible one.
AdvancedShow answer & explanation
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Q91. (a) State the classical definition of probability and the condition it requires, with an example where the condition fails. (b) Two coins are tossed. List the outcomes and find the probability of exactly one head, of at least one head, and of no heads. (c) Check that your three answers are consistent.
AdvancedShow answer & explanation
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Q92. (a) Prove that $0 \le P(E) \le 1$ and explain the meaning of each extreme. (b) Derive the complement rule. (c) A box contains 20 bulbs, 4 of which are defective. Find the probability that a bulb drawn at random is good, by two different methods.
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Q93. (a) Explain when the complement is worth using, and name the words that usually signal it. (b) Two dice are thrown. Find the probability that the total is 7, and hence that it is not 7. (c) Explain why listing the outcomes is the safest first step in this chapter.
AdvancedShow answer & explanation
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Q94. (a) Explain the difference between an outcome and an event, and between 'at least one' and 'exactly one'. (b) A bag contains 3 white and 9 black balls. Find the probability of drawing a white ball, and of drawing one that is not white. (c) Explain how the fact that all probabilities sum to 1 can be used as a check.
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Q95. With three coins, $P(\text{exactly two heads})$ is
AdvancedShow answer & explanation
$\frac38$
HHT, HTH and THH.
Q96. With three coins, $P(\text{at least one head})$ is
AdvancedShow answer & explanation
$\frac78$
$1 - \frac18$, since only TTT has no head.
Q97. For three coins, the head-counts 0, 1, 2 and 3 are
AdvancedShow answer & explanation
not equally likely
One head happens three ways, three heads only one.
Q98. Treating $(2,5)$ and $(5,2)$ as one outcome would give a total of
AdvancedShow answer & explanation
21 outcomes instead of 36
And every later answer would be wrong.
Q99. How many cards are either an ace or a face card?
AdvancedShow answer & explanation
16
12 face cards plus 4 aces, with no overlap.
Q100. How many cards are a king OR a heart?
AdvancedShow answer & explanation
16
4 kings and 13 hearts, but the king of hearts is in both lists.
Q101. Adding 4 and 13 to answer that question gives 17, which is wrong because
AdvancedShow answer & explanation
the king of hearts would be counted twice
Overlapping descriptions must not simply be added.
Q102. After that removal, how many hearts remain?
AdvancedShow answer & explanation
10
The hearts lose their jack, queen and king.
Q103. After that removal, $P(\text{a heart})$ is
AdvancedShow answer & explanation
$\frac14$
$\frac{10}{40}$ — the removal was symmetric across the suits.
Q104. Which method is quicker for 'at least one head' with three coins?
AdvancedShow answer & explanation
the complement
Only TTT fails, so one count replaces seven.
Q105. Two dice are thrown. $P(\text{a total of at least 11})$ is
AdvancedShow answer & explanation
$\frac{1}{12}$
Totals 11 and 12 give $2 + 1 = 3$ outcomes, so $\frac{3}{36}$.
Q106. One card is drawn from a pack. $P(\text{a black face card})$ is
AdvancedShow answer & explanation
$\frac{3}{26}$
Six such cards out of 52.
Q107. Assertion (A): Removing cards from a pack changes only the favourable count. Reason (R): The probability is the favourable count divided by the total number of cards available.
AdvancedShow answer & explanation
A is false but R is true
R is true and shows A false: the total available has changed as well.
Q108. Assertion (A): With two dice, a total of 7 is less likely than a double. Reason (R): Each can happen in six of the thirty-six outcomes.
AdvancedShow answer & explanation
A is false but R is true
Each happens in six of the thirty-six outcomes, so they are equally likely and the assertion is false. The reason gives the counts.
Q109. Explain why two dice give 36 outcomes rather than 21, and why it matters.
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Q110. How many cards in a pack are a king or a heart? Explain why the answer is not 17.
AdvancedShow answer & explanation
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Q111. All the face cards are removed from a pack and one card is drawn. Find the probability that it is a heart.
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Q112. Explain why the head-counts 0, 1, 2 and 3 are not equally likely for three coins.
AdvancedShow answer & explanation
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Q113. Two dice are thrown. Find the probability that the total is at least 11.
AdvancedShow answer & explanation
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Q114. (a) Explain why $n$ coins give $2^n$ outcomes, and list those for three coins. (b) Find the probability of exactly two heads, at least one head, and no heads. (c) Explain why the four possible head-counts are not equally likely.
AdvancedShow answer & explanation
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Q115. (a) Explain why two dice give 36 outcomes and why using 21 would be wrong. (b) Give the number of ways of making each total from 2 to 12. (c) Hence find the probability of a total of 7, of 12, and of at least 11.
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Q116. (a) Describe a pack of cards fully: suits, colours, ranks and face cards. (b) Find the probability of drawing a heart, a king, a red king and a black face card. (c) Explain why 'a king or a heart' is 16 cards rather than 17.
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Q117. (a) Explain what must change when cards are removed from a pack before a draw. (b) All the face cards are removed and one card is drawn. Find the probability that it is a heart, and that it is a king. (c) Explain why the first answer is unchanged from the full pack while the second is not.
AdvancedShow answer & explanation
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