Explanation : Petrol consumed during 1st year = 4000/8 = 500
Petrol consumed during 2nd year = 4000/10 = 400
Total expenditure = 4000 × 2 = 8000
Total petrol consumed = 500 + 400 = 900
Average cost per litre = 8000/900 = Rs 8.88
Note: The answer won’t be Rs 9 as many have
thought because calculation of average also
depends upon quantity consumed. This question
can be solved with harmonic mean also.