Places A and B are 20 km apart on the highway. A car starts from A and another from B at the same time. If the cars travel in the same direction at different speeds, they meet in one hour. If they traveled towards each other, they met in 12 minutes. What are the speeds (in km/h) of two cars?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is Option 1 i.e. 60, 40.
Let the speed of the car starting from A be x km/h, and the speed of the car starting from B be y km/h
Cars traveling in the same direction:
When the cars travel in the same direction, they meet after 1 hour. The relative speed when traveling in the same direction is x − y. In 1 hour, they cover a distance of 20 km
⇒ x - y = 20 km/hr......(1)
Cars traveling towards each other
When the cars travel towards each other, they meet after 12 minutes, which is 12/60 = 1/5 hours.
The relative speed when traveling towards each other is x + y, and the distance covered in 1/5 hours is 20 km
⇒ x + y = 20/1/5 = 20 × 5 = 100 km/hr......(2)
Now, adding eq 1 and 2
⇒ 2x = 120
⇒ x = 60 and y = 40
The two possible speeds of the cars are 60 km and 40 km/h