Percent Review

Percent Review

Converting Decimals to Percentages

When converting decimals to percents, move the decimal point two places to the right.

For example: .15 = 15%

Multiple Choice

Change to a percent:
0.05

• 50%
• .5%
• 5%
• 500%

Multiple Choice

Change to a percent:
0.36

• 36%
• 360%
• 3.6%
• .36%

Finding Percentages

When trying to find a stated percent of a whole, simply turn your percent into a decimal by moving your decimal two places to the left and multiply.

For example: 50% of 30

50% should become .50

.50 times 30 = 15

Multiple Choice

Find  $25\%$  of  $16$  

•  $1.6$  

•  $8$  

•  $4$  

•  $\frac{16}{25}$  

Multiple Choice

What is 60% of 40?

• 2400
• 66.7
• 16
• 24

Finding Percentages

When you know the percentage and the part you can use this information in the form of a proportion to solve for the missing piece.

For example:

 $\frac{\%}{100}=\frac{Part}{Whole}$  
16 is what percent of 20?  Solve for x.
 $\frac{x}{100}=\frac{16}{20}$  Cross multiply and divide.
1600 = 20x
Divide by 20 on both sides and you should get 80%.

Multiple Choice

45 is what percent of 60?

• 75%

• 70%

• 25%

• 60%

Percents of Increase or Decrease

The percent of change is the percent that a quantity changes from the original amount.

When the amount goes up we say that it increases.

When the amount goes down we say that it decreases.

Percents of Increase

When the new amount is larger than the original we need to find the percent of increase using this formula.
 $\frac{New\ amount\ -\ original\ amount}{original\ amount}$   

For example: 10 inches to 25 inches

 $\frac{25\ inches\ -\ 10\ inches}{10\ inches}$ 
We subtract and then divide.

 $\frac{15}{10}$  = 1.5 x 100 = 150% increase

Percents of Decrease

Same idea as increase except you are subtracting the new amount from the original amount, like this:
 $\frac{Original\ amount\ -\ new\ amount}{original\ amount}$  

For example: 50 pounds to 35 pounds

 $\frac{50\ pounds\ -\ 35\ pounds}{50\ pounds}$  
 $\frac{15}{50\ }=.30\ x100\ =\ 30\%$  

Multiple Choice

Is it an increase or decrease?
12 inches to 36 inches

• Increase
• Decrease

Multiple Choice

Calculate the percent increase. Round to the nearest percent.

Original: 12

New: 15

• 20%

• 0.25%

• 0.2%

• 25%

Markups and Discounts

When calculating markups and discounts, start by finding out what the question is asking. The process to find the percentage is the same as we previously reviewed.

Remember: When it is a markup you ADD it to the original amount.

When it is a discount you SUBTRACT it from the original amount.

Multiple Choice

Find the cost of a CD for $14.50 with a markup of 30%

• $18.85

• $18.86

• $4.35

• $4.36

Multiple Choice

A $10 shirt is on sale for 25% off the price. What is the sale price of the shirt?

• $7.50
• $2.50
• $12.50
• $17.50

Simple Interest

Interest can be found by using the formula:

I=Prt or Interest = Principal x rate x time

For example: $600 at 5% for 2 years

600 x .05 x 2 = $60.00 for a new total of $660.00

Multiple Choice

Principal = $800
Interest Rate = 3.5%
Time = 2 years
Find the interest earned.

• 56
• 140
• 168
• 16.80

Multiple Choice

Determine the simple interest earned:  p= $2000  r= 4.6%  t= 4 years

• $2370.00
• $348.00
• $2368.00
• $368.00