Question

Mary mixes white paint and blue paint in the ratio 2:3 . She makes a total of 20 litres of paint. How much more blue paint does she need to add to the mixture so that the ratio of white paint and blue paint becomes 1:7 ?

Answer 1

An additional amount of blue is: 44 liters

Explanation:

We can solve this problem in the two steps:

First we will make proportion

w : b = 2 : 3 => w = 2 c and b = 3 c where c is coefficient of proportion

We know that we have a total of 20 l of paint, which mean>

w + b = 20 => 2 c + 3 c = 20 => 5 c = 20 => c = 20/5 = 4 => c = 4

w = 2 c = 2 · 4 = 8 liters

b = 3 · 4 = 12 liters

Now we will make second proportion:

w : (b + x) = 8 : (12 + x) = 1 : 7

When we multiply external and internal members we get:

12 + x = 8 · 7 => 12 + x = 56 => x = 56 - 12 = 44 liters

x = 44 liters

God with you!!!