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 P at 6:30 a.m. at a speed of 30 km/h. At what time will they meet?

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.

Distance covered by him from 6 a.m. to 6:30 a.m. = $$20\times\ \frac{30}{60}$$ =  10 km

Another person starts from Q towards P at 6:30 a.m. at a speed of 30 km/h.

Now at 6:30 a.m., both of the persons are in movement to cover (400-10 = 390 km).

Time taken by them to meet each other = $$\frac{390}{20+30}$$

= $$\frac{390}{50}$$

= 7.8 hours

=  7 hours 48 minutes [1 hour = 60 minutes then, 0.8 hour = 48 minutes.]

So the time will they meet = 6:30 a.m. + 7 hours 48 minutes

= 2:18 p.m.