Of how likely something is
Probability is a measurement, but of what?
Length, area and volume measure physical things. Probability measures likelihood.
↳ Will it rain? Will we win? The outcomes are known, the result is not.
📚 Chapter Learning Kit
Probability · Class 9 Mathematics
English 3 topics 167 leveled MCQs 60 flashcards 4 games Free
Shared by a Veda teacher · Generated with Veda AI · Oct 2026
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You know the options, not the result
What makes an event random?
Randomness means all the possible outcomes are known but none can be predicted.
↳ It is not ignorance of the rules — only of the outcome.
Subjective against objective
Two friends disagree about whether it will rain.
A judgement based on how someone reads the evidence is a subjective probability, and it varies from person to person.
↳ Both are useful; only one can be marked.
What could happen?
The question that comes before any probability.
The complete list of possible outcomes is called the sample space, written $S$.
↳ Each item on the list is one element of the sample space.
Complete, and no repeats
Two rules the list must obey.
Every possible outcome must appear, or the denominator of every probability is wrong.
↳ The number of elements is the sample size, written $n(S)$.
Coin, die, two coins, a match
Four sample sizes worth knowing by sight.
↳ Write the list out and the size counts itself.
📖 Smart notes
What you'll study, topic by topic
1
What Probability Measures, and How to Put a Number on It
Some questions have no fixed answer, only possibilities, and probability is the measurement built for them. Every likelihood is a number from 0 to 1, and there are exactly two honest ways of finding it: count what actual…
~40 min · full explanation, examples & memory tricks in the app
2
Sample Spaces and Events
Every probability question begins with a list: what could happen? That list is the sample space, and an event is simply part of it. Once both are written out and counted, the probability is one division — provided the ou…
~45 min · full explanation, examples & memory tricks in the app
3
Tree Diagrams and Several-Stage Experiments
When an experiment happens in stages, the outcomes multiply rather than add, and a tree diagram sets them out one route at a time with nothing left out. Multiplying the stage counts tells you how many routes there are; d…
~45 min · full explanation, examples & memory tricks in the app
❓ Leveled MCQ practice
Try the smart MCQs from this kit
167 questions laddered from warm-up to topper-level, each with an explanation. A taste:
Probability is a measurement of
Beginner
A How long something lasts
B How much space a shape covers
C How likely an event is
D How heavy an object is
Show answer & explanation
How likely an event is
Length, area and volume measure physical quantities; probability measures likelihood.
An event is described as random when
Beginner
A Nothing at all is known about it
B It never happens twice the same way
C It is certain to happen
D The possible outcomes are known but not which will occur
Show answer & explanation
The possible outcomes are known but not which will occur
You know a coin will land heads or tails; you do not know which.
Two friends give different answers to "will it rain today?", each from the weather they can see. Each is giving
Intermediate
A An experimental probability
B A subjective probability
C A theoretical probability
D A relative frequency
Show answer & explanation
A subjective probability
A judgement from how one person reads the evidence varies from person to person.
Which of these is not a random event?
Intermediate
A The result of a coin toss
B The face a die shows
C The sun rising tomorrow
D The winner of a lucky draw
Show answer & explanation
The sun rising tomorrow
The sun rising is certain, so there is no element of chance in it at all.
🃏 Flashcards
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60 flashcards in this kit — the app reviews them with spaced repetition so the right card returns on the right day.
🎮 Learning games
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Word Match
True False
Fill Blank
Word Scramble
Playable in the app
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