A container holds 4 quarts of diesel and 4 quarts of petrol. How many quarts of water must be added to the container to create a mixture that is 3 parts dieselto 5 parts water by petrol?  Choices
A) 4 / 3	B) 5 / 3	C) 7 / 3	D) 8 / 3	E) 10 / 3

Rationale: an alternate to the alligation method is the more direct / algebraic method : let x be the amount of petrol to be added . new total amount of water = 4 + x total amount of diesel = 4 new total = 4 + 4 + x = 8 + x final ratio required ( for petrol ) = 5 / ( 5 + 3 ) = 5 / 8 thus , ( 4 + x ) / ( 8 + x ) = 5 / 8 - - > solving for x you get x = 8 / 3 . d is thus the correct answer .
Answer: D