Question

64 is what percent of 40?

Answer 1

Think of 40 as 100% (even though it is not)

X will be the value we are looking for

 If 40 is 100%, so we can write it down as 40=100%. 

We know, that x is 64% of the output value, so we can write it down as x=64%

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1) 40=100%
2) x=64%
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40/x=100%/64%

40/x=100/64
(40/x)*x=(100/64)*x     
40=1.5625*x     -divide both sides of the equation by (1.5625) to get x-
40/1.5625=x 
25.6=x 
x=25.6

So we get;
64% of 40=25.6