How do you find a percent if the whole number is known?

Answer 1

A percentage is determined by two numbers and so can't be used on its own to determine either the numerator or the denominator

If you know the numerator, then you can get the denominator by dividing the numerator by the percent (as a decimal)

So if (exactly) 25% of X equals 3, so 3/.25 = 12

Sometimes you will need to round the result:

E.g. 43% of X equals 3, so 3/0.43 = 6.98

But we know that the denominator is a whole number, so we round this to 7.

Rounding of the percentage is also important for bigger numbers, so

If 10% of X equals 12, 12/.1 = 120. But also 12/121 = 10% (to the nearest whole percent)

If, on the other hand, you have the (whole number) denominator and the percentage (rounded to n significant figures) then the lowest and highest whole number numerators can be evaluated in a spreadsheet as:

lower limit: =CEILING((proportion-0.5*POWER(0.1,n))*denominator,1)

upper limit: =FLOOR((proportion+0.5*POWER(0.1,n))*denominator,1)

where the proportion is the percentage as a decimal.

Answer 2

Add two zeros and a percentage sign.

For example, 23 = 2300%.