A car owner buys petrol at Rs. 7.50, Rs. 8.00 and Rs. 8.50 per litre for three successive years. What approximately is the average cost per litre of petrol, if he spends Rs. 4000 each year?
A
Rs. 7.98
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B
Rs. 8
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C
Rs. 8.50
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D
Rs. 9
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Solution
The correct option is D Rs. 7.98 Given that he spends Rs. 4000 each year
The cost of the petrol in the first year is Rs. 7.50 per litre
Number of litres, he bought in the first year is 40007.5
The cost of the petrol in the second year is Rs. 8.00 per litre
Number of litres, he bought in the second year is 40008
The cost of the petrol in the third year is Rs. 8.50 per litre
Number of litres, he bought in the third year is 40008.5
Average cost =4000+4000+400040007.5+40008+40008.5
=1+1+117.5+18+18.5
=3×7.5×8×8.5(8)(8.5)+(7.5)(8.5)+(7.5)(8)
=1530191.75=7.98
Therefore the average cost per litre of pertrol is Rs. 7.98