Two types of fuels costing Rs. 21/litre and Rs. 24/litre are mixed such that the average cost of the resultant mixture is Rs. 22.50/litre. What should be the amount of first fuel in the mixture if the second fuel is 30 litres?
Solution
Correct Answer: Option D
Let the amount of first fuel be x litres
Cost of first fuel = Rs. 21/litre
∴ Total cost of first fuel = 21 × x = Rs. 21x
Amount of second fuel = 30 litres
Cost of second fuel = Rs.24/litre
∴ Total cost of the second fuel = 24× 30 = Rs. 720
Total amount of fuel = (x + 30) litres
Cost of resulting mixture = Rs. 22.50/litre
∴ Total cost of resulting mixture = 22.50 × (x + 30)
⇒ 21x + 720 = 22.50 × (x + 30)
⇒ 21x + 720 = 22.50x + 675
⇒ 1.5x = 45
⇒ x = 30 litres
∴ Amount of first fuel to be mixed = 30 litres
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