2002 General Studies, all questions
UPSC Prelims 2002 · General Studies
Question 78: Basic Numeracy
A bus is moving at 30 km/h, and a car is coming from behind at 50 km/h. How far apart are they if it takes 15 minutes for the car to catch up with the bus?
a5 km
b7.5 km
c12.5 km
d15 km
AnswerThe answer is (a).
The car gains on the bus at a relative speed of 50 - 30 = 20 km/h. In 15 minutes (1/4 hour) it closes 20 x 1/4 = 5 km, so the gap at the start was 5 km. For catch-up problems, the gap equals relative speed times the time taken: 20 km/h x 0.25 h.
Why each option is right or wrong
- (a) Right: 20 km/h x 0.25 h = 5 km.
- (b) 7.5 km would take 22.5 minutes at 20 km/h.
- (c) 12.5 km would take 37.5 minutes at 20 km/h.
- (d) 15 km would take 45 minutes at 20 km/h.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2002, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.