Question

The volume of ethyl alcohol and water must be mixed together to prepare 250 ml of 60% by volume of alcohol in water

Answer 1

60% by volume of alcohol solution means,each 100 ml of solution will have 60 ml ethyl alcohol.
ie 100 ml of the solution has 60 ml ethyl alcohol
We need to find out the volume of ethyl alcohol and water in 250 ml solution.

100 ml solution ------ 60 ml ethyl alcohol
=> 250 ml solution -------(60/100)*250
=150 ml of ethyl alcohol

Hence in a 250ml solution, there will be 150 ml ethyl alcohol.
Total solution is 250 ml. 150 ml of that is ethyl alcohol.
=> Amount of water in the solution = 250 - 150 = 100 ml

Therefore, Amount of ethyl alcohol in 250ml solution = 150 ml
Amount of water = 100 ml

Hope this helps :)