13 is 40% of what number

Translate

percent means parts out of 100 so 40%=40/100=0.4

'of' means multiply

13 is 40% of what

13=0.4 times what

divide both sides by 0.4

32.5=what

the number is 32.5

Its 32.5. How I got this answer is you would usually multiply 'that number' by 40%, but since we don't know it we divide 13 divided by 0.4 (40% in decimal form) and that gives you 32.5. And to check your answer you do 32.5 multiplied by 0.4 to get 13.