A start from P walk to Q a distance of 51.75 kilometer at the rate of 3.75 km an hour. An hour latter B starts from Q for P and walk at the rate of 4.25 km an hour. When and where will A meet B?

A has already gone 3.75 km when B starts of the remaining 48 km.
A walks 3.75 km and B walks 4.25 km in one hour in opposite direction i.e., they together pass over (3.75 + 4.25) = 8 km. in hour.
Therefore , 48 km. are passed over in 48/8= 6 hours.
∴ A meets B in 6 hours after B started and, therefore, they meet at a distance of (4.25 X 6 ) = 25.5km. from Q.