Averages Q.5

5A car owner buys petrol at Rs 8 and Rs 10 for two successive years. What approximately is the average cost per litre of petrol if he spends Rs 4000 each year?

Option : C
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.

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