FINDING PERCENT OF A NUMBER

A percent is equivalent to the ratio of a part to a whole. To find a percent of a number, you can write a ratio to represent the percent, and find an equivalent ratio that compares the part to the whole.

We can find percentage of a number using the two methods given below. 

1.  Proportional reasoning 

2.  Methods

For example, to find 30% of 400, we can use :

Examples

Example 1 :

Use proportional reasoning to find 28% of 25.

Solution :

Step 1 : 

Write a proportion comparing the percent to the ratio of part to whole.

? / 25  =  28 /100

Notice that 25 is a factor of 100.

Step 2 :

Find the multiplication factor.

Since 25 · 4  =  100, find what number times 4 equals 28.

Step 3 :

Find the numerator.

7 / 25  =  28 /100

(Since 4 x 7 = 28,  28% of 25 = 7)

Hence, 28% of 25 is 7.

Example 2 :

Use multiplication to find 35% of 60.

Solution :

Step 1 : 

Write the percent as a fraction.

35% of 60  =  (35/100) of 60

Step 2 :

Always the word "of" is translated to "Multiplication" in Math. 

Multiply : 

35% of 60  =  (35/100) x 60

=  2100 / 100

=  21

Hence, 35% of 60 is 21.

Example 3 :

A sports store received a shipment of 400 baseball gloves. 30% were left-handed. How many left-handed gloves were in the shipment ?

Solution :

Step 1 : 

Write the percent as a fraction.

30% of 400  =  (30/100) of 40

Step 2 :

Always the word "of" is translated to "Multiplication" in Math. 

Multiply : 

30% of 400  =  (30/100) x 400

=  12000 / 100

=  120

Hence, 120 left-handed gloves were in the shipment.

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