Question

A car owner buys petrol at Rs. 7.50 Rs. 8.00 and Rs. 8.50 per litre for the 3 successive years. If he spends Rs. 4000 each year, then the average cost per litre of petrol is

Answer 1

for first year,

rate of petrol is 7.5 rs

so total petrol purchased = 4000 / 7.5 liters

for second year,

rate of petrol is 8 rs

so total petrol purchased = 4000 / 8 liters

for third year,

rate of petrol is 8.5 rs

so total petrol purchased = 4000 / 8.5 liters


total petrol purchased = 4000 / 7.5 + 4000 / 8 + 4000 / 8.5

= 4000 ( 1/7.5 + 1/8 +1/8.5)

now for three years total cost for purchasing petrol is 12000

so average = 12000 / 4000 ( 1/7.5 + 1/8 +1/8.5)

= 3 / ( 1/7.5 + 1/8 +1/8.5)

= 3/ ( 191.75 /510)

= 3 × 510 / 191.75

= 1530 / 191.75

= 7.9791 rs / liter