50 trees are standing in a line such that distance between any two consecutive trees is same. A car takes 18 seconds to travel from 13th tree to 34th tree. How much time (in seconds) will it take to reach from the first tree to the 50th tree?

Distance between two consecutive trees = 1

metre (let)

∴ Distance between 13th and 34th tree

= 34 – 13 = 21 metre

$\therefore$ Speed of car $=\left(\frac{21}{18}\right) \mathrm{m} . / \mathrm{sec} .=\frac{7}{6} \mathrm{~m} . / \mathrm{sec} .$

Distance between first and 50th tree = 49 metre

$\therefore$ Required time $=\left(\frac{49}{\frac{7}{6}}\right)$ seconds

$=\left(\frac{49 \times 6}{7}\right)$ seconds $=42$ seconds