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Question

An empty fuel tank of a car was filled with A type petrol. When the tank was half-empty, it was filled with B type petrol. Again when the tank was half-empty, it was filled with A type petrol. When the tank was half-empty again, it was filled with B type petrol. What is the percentage of A type petrol at present in the tank?

A. 33.5%

B. 37.5%

C. 40%

D. 50%

Comments

B) $37.5$%

Answer 1

At first tank is filled with 100 % type A petrol. 

 

Type A petrol in %	Type B petrol in %	Emptying tank
100	0	1st time empty half then fill with type B petrol
50	50	2nd time empty half then fill with type A petrol
75	25	3rd time empty half then fill with type B petrol
37.5	62.5

So,at end A type petrol will be 37.5%.
 

Comments

In the 3rd case how you determined that 75% for A and 25% for B. Because it is not given in question by how much proportion of A the fuel gets used every time when the tank is half emptied again.

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composition won't change irrespective of what part fuel used.