A takes 3 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 (in hours) does A require to walk 'd' km ?

8

Let speed of A = x km/h & Speed of B = y km/h

According to question ,

\(\frac{d}{x}\) - \(\frac{d}{y}\) = 3 hours      ----------(1)

And

\(\frac{d}{y}\) - \(\frac{d}{2x}\) = 1 hours       ------(2)

By adding equation 1 & equation 2 .

\(\frac{d}{2x}\) = 4

\(\frac{d}{x}\) = 8

So , A required 8 hours to walk 'd' cm.