Question

$A$ takes $2$ hours more than $B$ to walk $d$ km. If $A$ doubles his speed, then he can make it in $1$ hour less than $B.$ How much time does $B$ require for walking $d$ km?

• A. $\frac{d}{2}$ hours
• B. $3$ hours
• C. $4$ hours
• D. $\frac{2d}{3}$ hours

Answer 1

The correct option is C $4$ hours

Suppose B takes t hours to walk d km.
Then, A takes (t + 2) hours to walk d km.
With double speed, A will take $\frac{1}{2}(t+2)$ hours.
$\therefore t-\frac{1}{2}(t+2)=1\Rightarrow 2t-(t+2)=2\Rightarrow t=4$
$\therefore$ B takes 4 hours to walk d km.