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Official PYQ · 2023

GATE CS 2023 Q7 — General Aptitude

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Consider two functions of time (t),(t),
f(t)=0.01t2g(t)=4t\begin{gathered} f(t)=0.01 t^2 \\ g(t)=4 t \end{gathered}
where 0<t<∞.0<t<\infty.

Now consider the following two statements:

  1. For some t>0,g(t)>f(t)t>0, g(t)>f(t).
  2. There exists a T,T, such that f(t)>g(t)f(t)>g(t) for all t>Tt>T.

Which one of the following options is TRUE?\text{TRUE}?

Choose one option
View worked solution

Answer: C

We are given two functions of time tt for 0<t<∞0 < t < \infty:

f(t)=0.01t2f(t) = 0.01 t^2 g(t)=4tg(t) = 4 t

Let us analyze each statement:

Statement (i): For some t>0t > 0, g(t)>f(t)g(t) > f(t)

We want to find if there exists any t>0t > 0 such that:

4t>0.01t24t > 0.01 t^2

Since t>0t > 0, we can divide both sides by tt:

4>0.01t  ⟹  t<4004 > 0.01 t \implies t < 400

Thus, for any tt in the interval (0,400)(0, 400), g(t)>f(t)g(t) > f(t). For example, at t=1t = 1, g(1)=4g(1) = 4 and f(1)=0.01f(1) = 0.01, which satisfies g(1)>f(1)g(1) > f(1). Therefore, Statement (i) is correct.

Statement (ii): There exists a TT such that f(t)>g(t)f(t) > g(t) for all t>Tt > T

We want to find a threshold TT such that for all t>Tt > T:

0.01t2>4t0.01 t^2 > 4t

Since t>0t > 0, dividing both sides by tt gives:

0.01t>4  ⟹  t>4000.01 t > 4 \implies t > 400

If we choose T=400T = 400, then for all t>Tt > T, the inequality f(t)>g(t)f(t) > g(t) holds. Therefore, Statement (ii) is correct.

Since both statements (i) and (ii) are correct, the correct option is C.

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