CAT 2020 Quant Question [Slot 1] with Solution 06

Let the length of the train be l and its speed be s. Given \(\frac{l}{{(s - 2) \times \frac{5}{{18}}}} = 90;\frac{l}{{(s - 4) \times \frac{5}{{18}}}} = 100\)

\( \Rightarrow 90(s - 2) \times \frac{5}{{18}} = 100(s - 4) \times \frac{5}{{18}} \Rightarrow s = 22\)

\(\therefore \) Length of the train =500 m.

Hence the required time to cross a lamp post \( = \frac{{500}}{{22 \times \frac{5}{{18}}}}\)

i.e., 81.81 (or) 82 sec.