Arvind starts walking at 2 p.m. with the speed of 5 km/hr from P to Q.
Gopal goes on cycle at 3 p.m. with 10 km/hr from P to Q.
At what time Gopal will cross Arvind ?
Suppose, Gopal will cross Arvind after hour of Gopal's start.
Now, distance covered by Arvind = $(5 + 5/t)$ km
and distance covered by Gopal = $10/t$ km
Thus, $5 + 5/t = 10/t$ or $5=5/t$ or t = 1 hr.
Hence, Gopal will overtake Arvind at (3 + 1) p.m. = 4 p.m.