CMAT 2017 Solved Question Paper

(b) Let time taken by A to complete 400m = t sec
So, time taken by B to complete 400 m race = $\left(\mathrm{t}+\frac{50}{7}\right)$sec
Also, it is given that A beats B by 15m and gives hima start of 5 sec.
therefore, $\frac{385}{\mathit{t}+5}=\frac{400}{\mathit{t}+\frac{50}{7}}$
⇒385$\left(\mathit{t}+\frac{50}{7}\right)$ = 400(t+5)
⇒385t + 2750 = 400t + 2000
⇒15t = 150
⇒ t = 50 sec
therefore, Speed of A = $\frac{400}{50}$ = 8 m/s