Question

Town A and Town B are 100 km apart.

At 0800, James departs for Town B from
Town A, driving at a constant speed of
60 km/h. At 0830, Kumar departs for Town A
from Town B, driving at a constant speed of
50 km/h along the same route. What time
will James and Kumar pass each other?

Please help, thank you!

Answer 1

• 09 : 08 : 12

Explanation:

James travels 30 min before Kumar starts to travel.

By this time James travels:

• 60 km/h *30 min =
• 60 km/h * 0.5 h = 30 km

At 8:30 the distance between them is:

• 100 km - 30 km = 70 km

Time to travel 70 by both:

• 70 km / (60 + 50) km/h =
• 70 /110 h =
• 7/11 h ≈ 38.2 min

James and Kumar pass each other at:

• 08:30 + 38.2 =
• 09: 08.2

or

• 09 : 08 : 12

Answer 2

Distance between them=100km

James started at 8:00 and Kumar at 8:30

Time difference=30min

Now apply physics

Time=30min

Speed=60km/h

`\\ \rm\longmapsto Distance=Speed(Time)`

`\\ \rm\longmapsto Distance=60* (1)/(2)h=30km`

Now

Distance left =100km-30km=70km

Again

Distance=70km

Speed=60+50=110km/h

`\\ \rm\longmapsto Time=(Distance)/(Speed)=(70)/(110)\approx38min`

Now assumed time=8:30+0:38=9:08(approx)

Both will cross each other at 9:08