Question

When using a 1% cream and a 6% cream to produce a 4% cream, how many parts of each initial ingredient will be needed?

Answer 1

Here's visual way to calculate, which will let you do it mentally:

given cream concentrations
<b>1%</b> ----- 4% ----- <i>6%</i>
----<i>3%</i>--------<b>2%</b>---- Difference

Then you take 2 parts of 1% and 3 parts of 6% to get 4%.