Section A — MCQ (Single Correct)
Question 1
The coefficient of $x^4$ in the expansion of $\left(\frac{x}{2} - \frac{3}{x^2}\right)^{10}$ is:
A
$\frac{405}{256}$
B
$\frac{405}{512}$
C
$\frac{105}{256}$
D
$0$
Question 2
The total number of terms in the expansion of $(x + y + z)^{15}$ after combining like terms is:
A
$16$
B
$120$
C
$136$
D
$225$
Question 3
The middle term in the expansion of $\left(2x - \frac{1}{2x}\right)^{12}$ is exactly:
A
$\binom{12}{6}$
B
$-\binom{12}{6}$
C
$2^6 \binom{12}{6}$
D
$0$
Question 4
The value of the coefficient sum series $C_1 + 2C_2 + 3C_3 + \dots + 10C_{10}$ for $n=10$ is:
A
$10 \cdot 2^9$
B
$10 \cdot 2^{10}$
C
$5 \cdot 2^{10}$
D
$9 \cdot 2^9$
Question 5
The term independent of $x$ in the expansion of $\left(x^2 + \frac{1}{x}\right)^{9}$ occurs at which index value $r$?
A
$3$
B
$6$
C
$4$
D
No such constant term exists
Question 6
If the expression $(1+x)^n = C_0 + C_1x + \dots + C_nx^n$, the value of the fractional sum $\frac{C_0}{1} + \frac{C_1}{2} + \dots + \frac{C_n}{n+1}$ is:
A
$\frac{2^{n+1}-1}{n+1}$
B
$\frac{2^n}{n+1}$
C
$\frac{2^{n+1}}{n+1}$
D
$0$
Question 7
The coefficient of $a^3 b^2 c^1$ in the multinomial expansion of $(a + b + c)^6$ is:
A
$60$
B
$120$
C
$30$
D
$6$
Question 8
For a small value of $x$ ($x \ll 1$), the rational binomial expression $\frac{1}{(1-x)^2}$ can be linearly approximated as:
A
$1 + 2x$
B
$1 - 2x$
C
$1 + x$
D
$1 - x$
Question 9
The sum of the squares of the binomial coefficients $\sum_{r=0}^{5} \binom{5}{r}^2$ is equal to:
A
$\binom{10}{5}$
B
$2^{10}$
C
$32$
D
$\binom{10}{2}$
Question 10
The value of the alternating sum $C_0 - C_1 + C_2 - C_3 + \dots + (-1)^n C_n$ is:
A
$2^n$
B
$0$
C
$2^{n-1}$
D
$-1$
Section B — Integer Type
Question 11 — Integer answer
Find the value of $n$ if the coefficient of the second, third, and fourth terms in the expansion of $(1+x)^n$ form an Arithmetic Progression (AP).
Question 12 — Integer answer
Determine the remainder when the number $5^{99}$ is divided by 13.
Question 13 — Integer answer
Evaluate the value of the index $r$ that yields the greatest binomial coefficient in the expansion of $(1+x)^{12}$.
Section C — Assertion & Reasoning
Question 14 — Assertion / Reason
Assertion (A): The total number of terms in the expansion of $(x+y)^{20}$ is exactly 21.
Reason (R): The binomial expansion of $(a+b)^n$ starts at $r=0$ and ends at $r=n$, which creates exactly $n+1$ distinct terms.
A
Both A and R are true and R is the correct explanation of A
B
Both A and R are true but R is NOT the correct explanation of A
C
A is true but R is false
D
A is false but R is true
Solution: Both A and R are true and R is the correct explanation.
Question 15 — Assertion / Reason
Assertion (A): The sum of the coefficients of the odd terms equals the sum of the coefficients of the even terms in any positive integer binomial expansion.
Reason (R): Setting $x = -1$ in the identity equation $(1+x)^n = C_0 + C_1x + C_2x^2 + \dots$ forces the total alternating sum to equal exactly zero.
A
Both A and R are true and R is the correct explanation of A
B
Both A and R are true but R is NOT the correct explanation of A
C
A is true but R is false
D
A is false but R is true
Solution: Both A and R are true and R is the correct explanation.