+/- Decimals
State the rules of adding decimals.
1. Put largest number on top
2. Make sure decimals line up
3. Use zeros as placeholders
4. Add
Make sure to bring the decimal straight down in the same place!
6.24 x 0.375 =
2.34
6.24 ---- 2 decimal places
x .375 --- +3 decimal places
= 2.34000 ---- move decimal over 5 places total
1. Remove % sign
2. Move decimal to the left 2 places
3. 28% = 0.28
Note: 28% = 28 divided by 100 = 0.28
What is the formula to find the % of change?
new - old
old
Find the amount of simple interest earned and the new account balance:
Principal: $350
Annual Rate: 3.5%
Time: 5 years
$61.25 and $411.25
$350 x .035 (%) = $12.25
$12.25 x 5 years = $61.25
$350 (original balance) + $61.25 (simple interest) = $411.25
1.2 + 0.67 =
1.87
1.20
+ 0.67 = 1.87
How many places will the decimal have to move over in my answer?
3.348 x (-0.9) =
4 places
3.348 --- 3 places
-0.9 ---- 1 place = 4 places total
Explain how to write 28% as a fraction.
1. Remove % sign
2. Write as fraction 28/100
3. Simplify (if you can)
4. 28/100 = 7/25
What is the new? What is the old?
A flower grew 60 inches to 85 inches
New: 85 inches
Old: 60 inches
Find the amount of simple interest earned:
Principal: $1350
Annual Rate: 3.5%
Time: 1.5 years
$70.88
$1350 x .035 = $47.25
$47.25 x 1.5 years = $70.875 (round up)
Name the steps to subtract decimals properly.
1. Put largest number on top
2. Line up decimals
3. Use zeros as placeholders
4. Subtract
Make sure to bring down the decimal in the same place!
18.91 divided by 9.455 =
2
Write the percent as a decimal:
3.8%
0.038
Note: move the decimal 2 places to the left
Find the percent increase:
90 to 220
144%
220 - 90 = 130 = 1.444
90 90
Move decimal to the right twice
Round to the nearest percent: 1.444 = 144%
Find the balance of the account that earns interest compounded annually:
Principal: $2000
Annual Rate: 5%
Time: 36 months
$2315.25
2000(1 + 0.05)3
2000(1.05)3
2000(1.157625) = $2315.25
3.16 - 1.845 =
1.315
3.160
- 1.845 = 1.315
Explain the steps to divide the decimals below:
66.96 divided by 2.7 =
1. Set up decimals in long division format
2. Move decimal in 2.7 over once to the right to make 27
3. Move decimal in 66.96 over once to the right to make 669.6
4. Bring decimal from 669.6 up into answer
5. Divide as you normally would to get 24.8
Write the decimal as a percent:
-0.507
-50.7%
Hint: Move decimal to the right 2 places
Find the percent of change:
12,200 voters to 13,908 voters
14% increase
13,908 - 12,200 = 1,708 = .14
12,200 12,200
Move decimal to the right twice
.14 = 14%
Find the balance of the account that earns interest compounded annually:
Principal: $750
Annual Rate: 4.2%
Time: 8 years
$1042.32
750(1 + .042)8
750(1.042)8
750(1.38976622) = $1042.32
90.3 - (-7.81) =
98.11
90.3 - (-7.81) =
90.3 + 7.81 = 98.11
21.726 divided by 4.26 =
5.1
Write fraction as a percent:
3/5
60%
3 divided by 5 = 0.6
Move decimal over twice to the right
0.6 = 60%
Find the new amount:
50 is decreased by 30%
35
First, find 30% of 50 --> 50 x .30 = 15Then, subtract answer from 50
50 - 15 = 35
You borrow $700 at an annual simple interest rate of 4%. How much interest do you owe after 6 months?
What's your new balance after 6 months?
$14, $714
700 x .04 = 28
28 x .5 = 14
700 + 14 = $714
At 8am, the temperature outside was 65.2 degrees. By noon, the temperature had increased by 8.5 degrees. At 6pm, the temperature was 5.1 degrees cooler than at noon. What was the temperature at 6pm?
68.6 degrees
65.2 + 8.5 = 73.7
73.7 - 5.1 = 68.6
A tiger at a zoo has as mass of 144.9 kilograms. This is 40.25 times the mass of a certain house cat. What is the mass of the house cat?
3.6 kg
144.9 divided by 40.25
= 3.6 kg
Write percent as a fraction:
228%
2 7/25
228% = 2.28 = 2 28/100
2 28/100 --> simplify
= 2 7/25
A moving van is carrying a load that weighs 225 pounds. They pick up more furniture and the weight increases 44%. How much does the load weigh now?
324 pounds
Find 44% of 225 --> 225 x .44 = 99
Add answer to 225 --> 225 + 99 = 324
You deposit $3000 in a savings account for college that pays 4.5% interest compounded annually. What is the balance of the account after 8 years?
$4266.30
3000(1 + .045)8
3000(1.045)8