**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.

The formula given below can be used to find the percent increase or decrease of a value.

The change may be an increase or a decrease.

Here, the original amount is the value before increase or decrease.

**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 %

Hence, 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 %

Hence, 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 %

Hence, 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 %

Hence, 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 %

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

After having gone through the stuff given above, we hope that the students would have understood, how to solve problems on percent increase or decrease.

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