UPSC Prelims 2010 · General Studies
Question 66: Basic Numeracy
A person travelled a distance of 50 km in 8 hours. He covered a part of the distance on foot at the rate of 4 km per hour and a part on a bicycle at the rate of 10 km per hour. How much distance did he travel on foot ?
AnswerThe answer is (b).
Let x km be walked at 4 km per hour and (50 - x) km be cycled at 10 km per hour. Total time: x/4 + (50 - x)/10 = 8. Multiplying by 20 gives 5x + 2(50 - x) = 160, so 3x = 60 and x = 20 km. Check: 20 km on foot takes 5 hours and 30 km by bicycle takes 3 hours, 8 hours in all. Remember: write time = distance / speed for each part and add them.
Why each option is right or wrong
- (a) 10 km on foot takes 2.5 h and 40 km by bicycle 4 h: 6.5 h, not 8.
- (b) Right: 5 h walking + 3 h cycling = 8 h.
- (c) 30 km on foot takes 7.5 h and 20 km by bicycle 2 h: 9.5 h.
- (d) 40 km on foot takes 10 h, already more than 8 h.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2010, General Studies, Series A. The paper on upsc.gov.in.