2023 · Q34
A runner completed a 40 km race in 3 hours. She changed her speed after completing each quarter of the distance such that the proportion of the speeds in the first, second, third and the fourth quarter is 9 : 3 : 4 : 5 respectively. How much time (approximately) did she complete the last quarter of the race?
General Mental Ability, Quantitative Aptitude and StatisticsNumber system and arithmetic
- A32 minutes
- B34 minutes
- C30 minutes
- D28 minutes
Explanation
Each quarter is 10 km. With speeds in the ratio 9:3:4:5, the times are in the inverse ratio 1/9:1/3:1/4:1/5, i.e. 20:60:45:36 (161 parts) of the total 180 minutes. The last quarter's time is therefore (36/161) x 180, which is approximately 40 minutes. None of the given options (28, 30, 32 or 34 minutes) matches this computed value of about 40 minutes. Note: the published key for this question is disputed.