csatmedium
The tank-full petrol in Arun’s motor-cycle lasts for 10 days. If he starts using 25% more everyday, how many days will the tank-full petrol last?
- A.5
- B.6
- C.7
- D.8
▶ Answer & Explanation
Correct answer: D. 8
If the consumption increases by 25%, the new consumption is 1.25 times the original. Since the total quantity of petrol is fixed, the number of days the petrol will last is inversely proportional to the consumption rate. Therefore, if the consumption increases by a factor of 1.25, the duration will decrease by a factor of 1/1.25, which is 0.8. Thus, the petrol will last for 10 days * 0.8 = 8 days.
Source: UPSC csat 2013