Percent help. Finding a percentage of an amount without a calculator.



The easiest way to find a percentage of an amount (without a calculator) is to use the 10% method. You always begin the 10% method by finding 10 first, and then use this to build up other amounts. To find 10% of a number, all you need to do is to divide your amount by 10.

Example 1

Find 10% of $64.

64 ÷ 10 =£6.40 (move your numbers one place over the decimal point)

Example 2

Find 10% of $720.

720 ÷ 10 = 72 (just take the zero off!)

Now once you have 10% you can use this to build up larger percentages.

Example 3

Find 30% of $620.

First find 10% of your amount.

10% = 62

so 3 × 62 = $186

Also, it is quite useful to find 5% of an amount, do this by halving the 10% amount.

Example 4

Find 15% of $24.

First find 10%.

10% = $2.40 (Do this by dividing by 10)

Next find 5%.

5% = $1.20 (because half of $2.40 is $1.20)

Now if we add 10% and 5% together, this will give 15%.

S0 $2.40 + $1.20 = $3.60.

Let’s take a look at a real life example.

Example 5

In a zoo there are 840 animals. 45% of the animals are reptiles, and the rest are birds. How many reptiles are at the park? Also find out how many birds are at the zoo.

First find 10%, and then 5%.

10% = 84 (since 840 ÷ 10 =84)

5% = 42 (since half of 84 is 42)

Now to make 45% we need four 10 percents and one 5 percent.

So 84 × 4 + 42 = 336 + 42 = 378.

Therefore there are 378 at the zoo.

To find out how many animal are birds, just take 378 from 840. This gives 462 birds.

Summary

To get 10% divide by 10.

To find 5%, half the 10% amount.

Sometimes you might need 1%, do this by dividing by 100. Have a look at my other math pages to find 1%.