Question 141354
This is the same as making the following equation:
42=.4x
or in words
42 is 40% (.4) of what number (x)?

We can solve this simply without a calculator:

{{{42=(2/5)x}}}
{{{42(5/2)=x}}}
{{{21(5)=x}}}
{{{105=x}}}

Check:
105*2/5=210/5=42