1
IAT (IISER) 2025
MCQ (Single Correct Answer)
+4
-1

Let $S_n$ denote the sum of the first $n$ terms of a sequence $a_1, a_2, a_3, \ldots$. If $S_{n+3}-S_n=13 n+7$ for all $n$, what is the value of $a_{13}-a_{10}$ ?

A

13

B

137

C

46

D

12

2
IAT (IISER) 2025
MCQ (Single Correct Answer)
+4
-1

Five fair coins are tossed independently. What is the probability that at least two heads appear?

A

$\frac{13}{16}$

B

$\frac{7}{16}$

C

$\frac{5}{16}$

D

$\frac{11}{16}$

3
IAT (IISER) 2025
MCQ (Single Correct Answer)
+4
-1

Let $f: \mathbf{R} \rightarrow \mathbf{R}$ be the function defined by

$$ f(x)= \begin{cases}x^2-4 x-5 & \text { if } x \geq 1, \\ 2 x & \text { if } x<1 .\end{cases} $$

Which one of the following statements is TRUE?

A

$\quad f$ is onto but not one-one

B

$\quad f$ is one-one but not onto

C

$f$ is neither one-one nor onto

D

$f$ is one-one and onto

4
IAT (IISER) 2025
MCQ (Single Correct Answer)
+4
-1

Which one of the following is the solution of the differential equation

$$ x^2 \frac{d y}{d x}+9 x y=x^4(\text { for } x>0) $$

given that $y=0$ when $x=1$ ?

A

$\quad 12 y=x^3-\frac{1}{x^9}$

B

$\quad 12 y=x^9-\frac{1}{x^3}$

C

$9 y=x^{21}-\frac{1}{x^3}$

D

$\quad 9 y=x^3-\frac{1}{x^{21}}$

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