Finding the Percent of an Increase (Part I)



Finding the Percent of an Increase (Part I)

We all know that prices change over time. The price of food has increased, the price of a movie ticket has increased, and the price of gasoline has increased. It goes on and on, we could make a list of all of the prices that have increased in the past few years.

When prices increase, we can figure out by what percentage they have actually increased. We call this the percent of an increase.

How can we figure out the percent of an increase?

To figure out the percent of an increase, we are going to need to compare prices and to compare the change or difference between those prices.

Let’s look at an example to better understand this.

Example

The price of a stamp many years ago was 5 cents. Today, the stamp has increased to be 43 cents. That is a huge increase. What is the percent of the increase?

To solve this problem, we are going to need to work through a couple of steps.

1. Find the difference between the old price and the new price.

To do this, we subtract .43 - .05. Notice that we used the decimal money amounts to make our subtraction clearer.

.43 - .05 = .38

There is a difference of .38.

2. Next, we write a ratio to compare the difference or the amount of the change with the original price. We write the ratio in fraction form.

Amt of change /original price .38/ .05

. Next, we figure out the percentage. Our first step is to divide the numerator by the denominator.

3. Next, we figure out the percentage. Our first step is to divide the numerator by the denominator.

.38 ÷ .05 = 7.6

Now we can convert it to a percent by moving the decimal point two places to the right.

7.6 = 760 %

The percent of change is 760%. Wow! That is a HUGE increase!!

Let’s look at another example.

Example

Two years ago a movie ticket cost $5.50. Today it costs $8.50. What is the percent of the increase?

Let’s work this through by following the steps.

1. Find the difference between the original cost and the new cost.

We write this as an equation that we can solve.

8.50 – 5.50 = $3.00

2. Write a ratio. We need to write a ratio that compares the difference between the old and new cost and the original price. We write this ratio as a fraction. We divide the numerator by the denominator to get a decimal answer, = .55 3.00 5.50

3. Next, we write the decimal as a percentage.

Move the decimal point two places to the right to represent the hundredths place, .55 = 55 %.

Our answer is 55%

Finding the Percent of an Increase Worksheet

Directions: Find the percent of each increase.

1. Old price = $5.00

New price = $7.00

% of increase=

2. Old price = $8.00

New price = $12.00

% of increase=

3. Old price = $.50

New price = $2.00

% of increase=

4. Old price = $.75

New price = $1.50

% of increase=

5. Old price = $2.25

New price = $6.35

% of increase=

6. Old price = $45.00

New price = $89.00

% of increase=

7. Old price = $2000.00

New price = $3500.00

% of increase=

8. Old price = $350.00

New price = $700.00

% of increase=

9. Old price = $1800.00

New price = $3500.00

% of increase=

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