Class IX Maths SA-1: Number Systems, Polynomials, Coordinate Geometry, Linear Equations & Lines and Angles: 20 MCQs with answers
All 20 multiple-choice questions from this kit, free and with no sign-up.
Warm-up · 8 questions
Q1. Which of the following is an example of an irrational number?
BeginnerShow answer & explanation
$1.101001000\ldots$
$1.101001000\ldots$ is non-terminating and non-repeating, so it is irrational. The others are terminating or repeating decimals, hence rational.
Q2. How many rational numbers lie between $\frac{1}{5}$ and $\frac{2}{5}$?
BeginnerShow answer & explanation
Infinitely many
Between any two rational numbers there are infinitely many rational numbers.
Q3. What is the coefficient of $x$ in $9x^2 + 4x - 6$?
BeginnerShow answer & explanation
$4$
The coefficient of $x$ is the number multiplying $x$, which is $4$.
Q4. Which of the following is a quadratic polynomial?
BeginnerShow answer & explanation
$ax^2 + bx + c$
A quadratic polynomial has degree $2$, so its standard form is $ax^2 + bx + c$.
Q5. If the $y$-coordinate of a point is zero, the point always lies:
BeginnerShow answer & explanation
On the $x$-axis
A point with $y = 0$ lies on the $x$-axis.
Q6. What is the standard form of a linear equation in two variables $x$ and $y$?
BeginnerShow answer & explanation
$ax + by + c = 0$
The standard form is $ax + by + c = 0$.
Q7. A ray that divides an angle into two equal angles is called:
BeginnerShow answer & explanation
Angular bisector
An angular bisector divides an angle into two equal angles.
Q8. Every rational number has either a terminating or a repeating decimal expansion, while every irrational number has a non-terminating, non-repeating decimal expansion.
BeginnerShow answer & explanation
True
Every rational number has either a terminating or a repeating decimal expansion, while every irrational number has a non-terminating, non-repeating decimal expansion.
Building up · 7 questions
Q9. Which of the following is a rational number?
IntermediateShow answer & explanation
$\sqrt{225}$
$\sqrt{225} = 15$, which is rational. $\sqrt{23}$ and $1.101001000\ldots$ are irrational.
Q10. Simplify: $(3 + \sqrt{3})(2 + \sqrt{2})$
IntermediateShow answer & explanation
$6 + 3\sqrt{2} + 2\sqrt{3} + \sqrt{6}$
Using distributive property: $3(2) + 3(\sqrt{2}) + \sqrt{3}(2) + \sqrt{3}(\sqrt{2}) = 6 + 3\sqrt{2} + 2\sqrt{3} + \sqrt{6}$.
Q11. Factorise: $y^2 - 5y + 6$
IntermediateShow answer & explanation
$(y - 2)(y - 3)$
Find two numbers that multiply to $6$ and add to $-5$: $-2$ and $-3$. So $y^2 - 5y + 6 = (y-2)(y-3)$.
Q12. Find the value of $k$ if $(x - 1)$ is a factor of $P(x) = kx^2 - 3x + k$.
IntermediateShow answer & explanation
$k = \frac{3}{2}$
By Factor Theorem, $P(1) = 0$. So $k(1)^2 - 3(1) + k = 0 \implies 2k - 3 = 0 \implies k = \frac{3}{2}$.
Q13. In which quadrant does the point $(-4, -1)$ lie?
IntermediateShow answer & explanation
Quadrant III
Both coordinates are negative, so the point lies in Quadrant III.
Q14. Express $5x + 2y = 2$ in the form $ax + by + c = 0$. What is $a + b + c$?
IntermediateShow answer & explanation
$5$
$5x + 2y - 2 = 0$, so $a=5$, $b=2$, $c=-2$. Then $a+b+c = 5+2-2 = 5$.
Q15. If $x = 0$, find the value of $y$ in $3x + 4y = 12$.
IntermediateShow answer & explanation
$y = 3$
Substitute $x=0$: $4y = 12 \implies y = 3$.
Topper level · 5 questions
Q16. If $x + y + z = 0$, then $x^3 + y^3 + z^3$ equals:
AdvancedShow answer & explanation
$3xyz$
When $x+y+z=0$, the identity $x^3+y^3+z^3-3xyz = \frac{1}{2}(x+y+z)[(x-y)^2+(y-z)^2+(z-x)^2]$ reduces to $x^3+y^3+z^3 = 3xyz$.
Q17. Given the linear equation $3x + 4y = 12$, if we express it in the form $ax + by + c = 0$, what is the value of $a^2 + b^2 + c^2$?
AdvancedShow answer & explanation
16
Rearranging $3x + 4y = 12$ gives $3x + 4y - 12 = 0$. Here, $a = 3$, $b = 4$, and $c = -12$. Thus, $a^2 + b^2 + c^2 = 3^2 + 4^2 + (-12)^2 = 9 + 16 + 144 = 169$.
Q18. If $x + y + z = 0$ and $x = 2$, $y = -3$, what is the value of $z^3$?
AdvancedShow answer & explanation
-27
From $x + y + z = 0$, substituting $x = 2$ and $y = -3$ gives $2 - 3 + z = 0$, leading to $z = 1$. Thus, $z^3 = 1^3 = 1$.
Q19. In a coordinate plane, if the point $A(-4, -6)$ is reflected across the y-axis, what are the coordinates of the reflected point?
AdvancedShow answer & explanation
(4, -6)
Reflecting across the y-axis changes the sign of the x-coordinate. Therefore, the coordinates of point $A(-4, -6)$ become $(4, -6)$.
Q20. If the angles $\angle AOC$ and $\angle BOC$ are given as $(3x + 10)^\circ$ and $(4x - 26)^\circ$ respectively, what is the value of $x$ if these angles form a linear pair?
AdvancedShow answer & explanation
28
Since $\angle AOC + \angle BOC = 180^\circ$, we have $3x + 10 + 4x - 26 = 180$. Simplifying gives $7x - 16 = 180$, leading to $7x = 196$, thus $x = 28$.
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