FINDING PERCENT INCREASE AND DECREASE

In our day to day life, often we may see the situations where the values will change.

For example,

Increase in wages

Increase/Decrease in price of an item

Increase/Decrease in temperature

In this section, we will learn the increase or decrease of a value in terms of percent.

That is, we will calculate, how much a value is increased or decreased per hundred.

For example, a laptop is originally priced $2500, but Richard gets it for $2250.

The actual decrease he gets in the price of the laptop is $250.

Here, the percent decrease is, how much the price is decreased per hundred.

In 2500, there are 25 hundreds.

For 25 hundreds (2500), he gets a decrease of 250.

Find the decrease for 1 hundred.

That is,

= 250/25

= 10

So, for each $100 of the price, he gets a decrease of $10.

This is called percent decrease.

Therefore, the price of the laptop is decreased by 10 percent.

Example 1 :

What is the percent increase from $5 to $8?

Solution :

Step 1 :

Find the amount of change.

Amount of change = Greater value - Lesser value 

= 8 - 5

= 3

Step 2 :

Percentage change is

= (Amount of change/Original amount) x 100 %

= (3/5) x 100%

= 0.6 x 100%

= 60%

So, the percent increase from $5 to $8 is 60%.

Example 2 :

Amber got a raise, and her hourly wage increased from $8 to $9.50. What is the percent increase?

Solution :

Step 1 :

Find the amount of change. 

Amount of change = Greater value - Lesser value 

= 9.50 - 8.00

= 1.50

Step 2 :

Find the percent increase. Round to the nearest percent.

Percentage change is 

= (Amount of change/Original amount) x 100 %

= (1.50/8.00) x 100%

= 0.1875 x 100%

= 18.75%

≈ 19%

So, Amber's hourly wage is increased by 19%.

Example 3 :

The price of a pair of shoes increases from $52 to $64. What is the percent increase to the nearest percent?

Solution :

Step 1 :

Find the amount of change. 

Amount of change = Greater value - Lesser value 

= 64 - 52

= 12

Step 2 :

Find the percent increase. Round to the nearest percent.

Percentage change is

= (Amount of change/Original amount) x 100 %

= (12/52) x 100%

= 0.2307 x 100%

= 23.07%

≈ 23%

So, the price of a pair of shoes increased by 23%.

Example 4 :

In a class, students strength has been increased from 20 to 30. What percent of strength is increased ?

Solution :

Step 1 :

Find the amount of change.

Amount of change = Greater value - Lesser value 

= 30 - 20

= 10

Step 2 :

Find the percent increase. Round to the nearest percent.

Percentage change is 

= (Amount of change/Original amount) x 100%

= (10/20) x 100%

= 0.5 x 100%

= 50%

So, the strength is increased by 50%.

Example 5 :

Mr. David monthly salary is revised from $2500 to $2600. What percentage is the salary increased?

Solution :

Step 1 :

Find the amount of change. 

Amount of change = Greater value - Lesser value 

= 2600 - 2500

= 100

Step 2 :

Find the percent increase. Round to the nearest percent.

Percentage change is 

= (Amount of change/Original amount) x 100%

= (100/2500) x 100%

= 0.04 x 100%

= 4%

So, David's monthly salary is increased by 4%.

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