A car owner buys a petrol car at Rs 750 and Rs 8 and Rs 8.50 per litre for three successive years. What approximately is the average cost per litre of petrol if he spends 4000 each year?

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Rs. 7.98

Rs. 8

Rs. 8.50

Rs. 9

answer is A.

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Detailed Solution

Concept- Applying the unitary method, in which we find out the value of a single unit from the value of multiple units and the value of multiple units from the value of a single unit. Here, we will find an approximate value of the average cost per litre of petrol if he spends 4000 each year.
Step 1- In first year, the car owner spends Rs 4000, and for which he buys = 4000/7.5 = 533.33 litres.
Step 2- In second year, he buys = 4000/8=500
Step 3- In third year, he buys = 4000/8.5=470.59 Step 4- Total litres of petrol which the car owner bought = 533.33 + 500 + 470.59 =1503.92 litres.
Cost of 1503.92 litres of petrol = 4000×3 = Rs 12000
Therefore, the average cost of petrol that he bought is = 12000/1503.92 = Rs 7.979 per litre.
= Rs 7.979 ≈ Rs 7.98 per litre.
The average cost per litre of petrol if he spends 4000 each year is Rs. 7.98.
Hence, the correct answer is option 1) Rs. 7.98

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