Question

A large container holds 14 litres of a solution which is 25% antifreeze, the remainder being water. How many litres of antifreeze must be added to the container to make a solution which is 30% antifreeze? NOTE: Only put number, DO NOT PUT any units or sentences.

Answer 1

2.8 liters

Explanation:

So there are various ways to do this problem, this is just MY preferred way.

Since we are given 1/4th of a total value with 14 liters, we can actually make this 4/4 by multiplying our given value by 4. In this case, 14 liters for 25% becomes 56 liters for 100% antifreeze.

Since we know have a percent of 100%, we can proceed to take 10% increments, all the way up to 30%

10% is 5.6, multiplied by 3 is 16.8

While you might want to put 16.8 instantly, don't forget we are looking for how much is ADDED from 25%, not just how much there is.

In this case, subtract 14 from 16.8 to come out with a grand total of 2.8 liters added.