The Usual Method
We have to simplify starting from the denominator value of
Estimated Time to arrive at the answer = 120 seconds.
You can simply approximate the expression (Note, that the actual value will be less than 5 and hence the ‘–’ sign in brackets)
Since, the actual denominator is less than 5, the final answer will be greater than 82. The only option coming close to this figure is 88, i.e option ‘2’.
Estimated Time to arrive at the answer = 10 seconds.