Name: Date: Period: 1 2 3 4

Adding & subtracting Decimals

You add and subtract decimals the same way you do whole numbers, after you line up the decimal points.

Adding & Subtracting Decimals /
  • Write the numbers you want to add or subtract so that the decimal points are in a line. Add zeros if they are needed. (Annex the zero)
  • Estimate the sum or difference so you can check to see if your final answer is reasonable.
  • If subtracting, regroup if necessary. Add or subtract. Compare the result with your estimate.

Cassie measured 27.5 inches of rain for the first six months of the year. She anticipates that the total rain count for the year will be 60 inches. How many more inches of rain are needed to make her prediction true?

Subtract 27.5 from 60.

Line up the decimal points and add a zero.

60.0Estimate first.

- 27.5This is about 60 – 30 or 30.

32.2This is reasonably close to the estimate of 30.

Adapted from Glencoe, Course 2

  1. 5.6 + 4.2
  2. 1.25 + 1.34
  3. 6 – 3.48
  4. 0.006 + 0.15
  5. $10.26 - $8.28
  6. What is the value of t – p if t = 2.73 and p = 1.1
  7. Solve for r: r = 9 – 6.7

Adapted from Glencoe, Course 2

  1. Alexis is 1.55 meters tall and Melina is 1.47 meters tall. How much taller is Alexis than Isabella?
  2. Rae bought four items costing $5.13, $1.98, $0.89, and $4.78, including tax. If he paid using a $20 bill, how much change did he receive?
  3. Ro’Kia is building a base for her new aquarium. She wants the length of the base to measure 9.25 inches, but the wood is only sold in 12 inch lengths. How much needs to be cut off to make the base the right length?

MULTIPLYING Decimals

Multiplying Decimals /
  • Place the number with the most digits on top.
  • Multiply.
  • Count the number of digits behind the decimal point in each factor. The number of decimal places in the product is the sum of the number of decimal places in the factors. Insert the decimal in the product.

Multiply. 0.26  3.4

0.26two decimal places

 3.4one decimal place

0.884 three decimal places

Adapted from Glencoe, Course 2

  1. 48 0.89
  2. 101.970.5
  3. $0.30  $68
  4. 5 0.62
  5. 5.2  6.88
  6. 312  1.6

Adapted from Glencoe, Course 2

  1. Isaac bought 6 digital video camcorders that cost $28.95 each. How much did the digital video camcorders cost altogether?
  2. Juan noticed that her favorite candy was on sale this week for $1.59 each. He decided to purchase 4 king size packs with 2 portions in each pack. Quincy saw the same candy on sale for $0.79 for a single portion. He convinced Juan that he saw a better deal. Explain what information and steps Quincy might have used to support his thinking. Did Quincy actually find the better deal? Explain why or why not?

DIVIDING Decimals

Dividing Decimals /
  • If necessary, change the divisor to a whole number by moving the decimal point to the right. (You are multiplying by a power of ten.)
  • Move the decimal point in the dividend the same number of places to the right. (You are multiplying by a power of ten.)
  • Bring the decimal point up into the quotient, if necessary.
  • Divide as with whole numbers.

Shanise swims the 50-meter freestyle for her swim team. Her best time is 29.51 seconds. To the nearest tenth, find her speed in meters per second.

50  29.51

Rewrite the division sentence.

Make the divisor a whole number by moving the decimal point two places to the right.

Divide as with whole numbers.

1.69  1.7 Round the answer to the nearest tenth.

Adapted from Glencoe, Course 2

  1. 28.96  8
  2. 19.2  32
  3. Evaluate ab if a = 38.4 and b = 60

Adapted from Glencoe, Course 2

  1. A can of soda costs $0.75. If the can holds 12 ounces, what is the cost of soda per ounce? Round your answer to the nearest cent.

Adapted from Glencoe, Course 2