Indian Institute of Foreign Trade 2009 Solved Paper

Question : 116 of 122

Marks: +1, -0

A petrol tank at a filling station has a capacity of 400 litres. The attendant sells 40 litres of petrol from the tank to one customer and then replenishes it with kerosene oil. This process is repeated with six customers. What quantity of pure petrol will the seventh customer get when he purchases 40 litres of petrol?

20.50 litres
21.25 litres
24.75 litres
22.40 litres

Validate

Solution:

From 2nd customer for each customer the purity of oil becomes 0.9 of it's previous value i.e. 2nd customer will get only

40×0.9=36

liters of pure petrol 3rd customer will get

36×0.9=32.4

liters of pure petrol and so on. Therefore the 7th customer will get

40×(0.9)^6=21.25

liters of pure petrol
Therefore our answer is option 'B'.

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