For every 1 cup of blue paint,
cups of red paint are needed
For every 1 cup of red paint,
cup of blue paint is needed
For every 4 cups of red paint,
cups of blue paint are needed
<em><u>Solution:</u></em>
Given that, there are 3 1/3 red cups of paint for every 1 1/3 cups of blue paint
Therefore, ratio is

<h3><u>For every 1 cup of blue paint, ___ cups of red paint are needed</u></h3>
Let "x" be the cups of red paint needed
Then we get,

This forms a proportion

Therefore, 10/4 cups of red are needed for 1 cup of blue
<h3><u>For every 1 cup of red paint, ___ cup of blue paint is needed</u></h3>
Let "x" be the cups of blue paint needed
Then, we get

This forms a proportion

Thus, 4/10 cups of blue are needed for 1 cup of red paint
<h3><u>For every 4 cups of red paint,___ cups of blue paint are needed</u></h3>
Let "x" be the cups of blue paint needed
Then, we get

This forms a proportion

Thus 16/10 cups of blue paint are needed for every 4 cups of red paint