Question

A and B started towards each other at the same time from two different places which is 123 km apart and met in 4 hours after they started. If the speed of A was 12 km/h, then what is the speed of B (in km/h)?
1. 18.25 km/h
2. 18.75 km/h
3. 16.50 km/h
4. 16.75 km/h

Answer 1

Correct Answer - Option 2 : 18.75 km/h

Given:

Distance between the two places = 123 km

Time taken to meet = 4 hours

Speed of A = 12km/h

Concept used:

When two objects traveling in the same direction,

Relative speed = |speed of A - speed of B|

When two objects traveled in the opposite direction,

Relative speed = |speed of A + speed of B|

Formula used:

Distance between the place = Relative speed × time

Calculation:

Distance between the place = Relative speed × time

⇒ 123 = (speed of A + speed of B) × 4

⇒ 123/4 = 12 + (speed of B)

⇒ Speed of B = 30.75 - 12 = 18.75 km/h

∴ Speed of B is 18.75 km/h.