AFCAT Model Paper 4

Given:
The quantity of alcohol in a 27 quartz capacity car radiator = 18%
Drained and Replace quantity = 90% alcohol solution
The resulting solution contains 90% alcohol
Calculation:
According to the question
We have to mix 18% alcohol solution with 90% alcohol solution to get a 42% alcohol solution.
Let’s assume that x quartz of 18% solution are mixed with y quartz of 90% solution.
Amount of alcohol in x quartz of 18% solution = 0.18x Quartz
Amount of alcohol in y quartz of 90% solution = 0.90y Quartz
Total amount of alcohol in x + y quartz = 0.18x + 0.9y
⇒ 0.42 (x + y) = 0.18x + 0.9y
⇒ 0.24x = 0.48y
⇒ x : y = 2 : 1
We know that, x + y = 27
⇒ x = 18 and y = 9
∴ 9 quartz of 18% solutions are drained and replaced with 90% solution.