What you need to know

 Things to remember:

  • You can add and subtract different percentages to make the percentage you want.

What is 50% of 80?

Well, we have a couple of ways of doing this. First, we should look back at how we write percentages as fractions.

Percent                       Fraction                       Division

100%               \dfrac{1}{1}           \div1

 50%                 \dfrac{1}{2}          \div2

25%                 \dfrac{1}{4}          \div4

 20%                 \dfrac{1}{5}          \div5

 10%                 \dfrac{1}{10}          \div10

     5%                   \dfrac{1}{20}            \div20

    2%                   \dfrac{1}{50}            \div50

       1%                    \dfrac{1}{100}        \div100

So, how do we find the 50% of 80? Well, the table tells us we have to divide by 2!

50\% \text{ of }80 = 80\div2=40

Not too bad, right?

What is 2% of 400?

The table tells us that to find 2% we have to divide by 50.

2\% of 400 = 400\div50=8

How about if we have to find a percentage that isn’t in our table? Well, we can do that 3 steps.

What is 35% of 200?

Step 1: Think about what percentages in our table we can add or subtract to make the percentage in the question.

 

35\% = 25\% + 10\%

Step 2: Find these new percentage amounts.

25\% of 200 = 200\div4=50

10\% of 200 = 200\div10=20

Step 3: Add or subtract the percentages.

We need to add ours.

35\% = 25\% + 10\%

35\% of 200 = 50 + 20 = 70

Now for the quick and exciting method, which we’d usually do using a calculator.

What is 37% of 400?

What is 37% as a fraction?

37\% = \frac{37}{100}

So, this question can actually be rewritten as:

What is \frac{37}{100} of 400?

But, we know how to do this in two steps:

Step 1: Divide the amount by the denominator.

400\div100=4

Step 2: Multiply the number in Step 1 by the numerator.

37\times4=148

37\% of 400 = 148

So, we can actually use these steps to find ANY percentage amount, even decimals!

What is 59 % of 300?

Step 1: Divide the amount by 100.

300\div100=3

Step 2: Multiply by your percentage.

 3\times59=177

59\% of 300 = 177

Example Questions

Question 1: What is 45% of 40?

Answer

Step 1: Think about what percentages in our table we can add or subtract to make the percentage in the question.

 

 45\% = 50\% - 5\%

 

Step 2: Find these new percentage amounts.

 

50\% of 40 = 40\div2=20

 

5\% of 40 = 40\div20=2

 

Step 3: Add or subtract the percentages.

 

We need to add ours.

 

45\% = 50\% - 5\%

 

45\% of 40 = 20 -2 = 18

Question 2:  What is 87% of 700?

Hint: Try using a calculator

Answer

Step 1: Divide the amount by 100.

 

700\div100=7

 

Step 2: Multiply by your percentage.

 

 7\times87=609

 

87\% \text{ of } 700 = 609