Points P and Q are 400 km apart. A person starts from P towards Q at 6 a.m. at a speed of 20 km/h. Another person starts from Q towards Pat 6:30 a.m. at a speed of 30 km/h. At what time will they meet?

2:18 p.m

Distance b/w P & Q is = 400 km

Distance = Speed ×  Time

Distance covered by man starting from P during 6 to 6:30am = 20 × \(\frac{1}{2}\)

= 10 km

Remaining distance = 400 - 10 = 390 km 

Relative speed ( When moves in opposite direction ) = 20 + 10 = 30 km/h

Time taken to meet = \(\frac{390}{30}\) = 7.8 hours

So , They will meet at = 6:30 am +  7 hours + 48 minutes = 2:18 pm