What is 25% of 90?

1 Answer
Apr 6, 2016

25% of 90 is 22.5.


A percent is any number over 100, so 25% is 25 over 100, this means that 25% can be written as:


Now, any number in fractional form (a number over a number) is the same as division so 25% can also be written as a decimal, we just move the decimal point 2 places to the right of 25, like this:

#25/100= 0.25#

Now we have two ways that we can solve this problem! I'll start with the fractional method of solving.


The Fractional Method

So we have a fraction: #25/100#, lets think, how many 25's do we need to get to 100? Well:

#25+25= 50#


#50+50= 100#

so that means,

#25+25+25+25= 100#


#25*4= 100#

This means that we need four 25's to get 100.


#25/100= 1/4#

(we could also divide both numerator and denominator by 5 to get the same result:

#25/100 div (5/5)= 5/20 div (5/5)= 1/4#

Now that we know 25% is equal to #1/4# we can either multiply 90 by #1/4# or we can divide 90 by 4, its easiest (for me anyway) to just divide 90 by 4.

#90 div 4= 22.5#


The Decimal Method

As we found out above 25% equals 0.25 so we can solve this problem using decimals too! All we need to do is multiply 90 by 0.25, which gives us the same answer as above.

#0.25*(90)= 22.5#


Despite the fact that that mathematics seemed to be a lot more involved in the fractional method, the calculations were a lot easier and personally I found it to be faster than the decimal method. The decimal method is great when you're working with fractions that aren't equal to 100 (For example: #3/7# of 21 is what number?) or when you have a calculator.

Sorry this is so long, I hope it helped though!