Question

40% of some number is 40

Answer 1

40% as a decimal is 0.4

"of" means to multiply

let "some number" be represented as "x"

"is" means equals

so we get   0.4*x = 40
solving for x:   x = 40 / 0.4 = 100

therefore your number would be  100

Answer 2

40% of the number 100 is 40.
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If you do it like this:
Change the percentege to a decimal it is: 
.4 (.40) Which is less than one whole. ( 1.00)
So, therefore the answer is 40% of 100 is 40
-Hope this helped :)