Decimals

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# Decimals - PowerPoint PPT Presentation

Decimals. Comparing Adding Subtracting Multiplying Dividing. Comparing Decimals. Which is the largest number? . 02   . 0201    . 021. Which is the largest number? . 02   . 0201    . 021. The easiest way to tell is to line them up vertically with the decimals over one another .02

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Presentation Transcript
Decimals
• Comparing
• Subtracting
• Multiplying
• Dividing
Comparing Decimals
• Which is the largest number?

.02   .0201   .021

Which is the largest number?.02   .0201   .021

The easiest way to tell is to line them up vertically with the decimals over one another .02

.0201

.021

Which is the largest number?.02   .0201   .021

And then add zeroes until they all have the same number of digits

.0200

.0201

.0210

Now, If you read them ignoring the initial zeroes, it should be obvious which is the biggest

- .0210 (which would read two-hundred-ten)

Place in order from least to greatest:
• 6.4   6.388   6.41

6.400 Six-thousand four-hundred

6.388 Six-thousand three-hundred eighty-eight

6.410 Six-thousand four-hundred ten

So, in order, they would be:

Order from least to greatest:
• 0.001   0.00102   0.0011

0.001

0.00102   Step one – line up vertically

0.0011

--------------

0.00100

0.00102   Step two – add zeroes

0.00110

0.00100

0.00102   Step 3 - Compare

0.00110

• 100, 102 and 110
• These numbers are already in order from least to greatest
• To add decimals simply line them up vertically with the decimals over one another, bring the decimal straight down into the answer line, and then add as usual.
• Example: 5.321 + 2.397

5.321

+2.397

7.718

Subtracting Decimals
• To subtract decimals simply line them up vertically with the decimals over one another, bring the decimal straight down into the answer line, and then subtract as usual.
• Example: 0.45 - 0.28

Again, it’s just the same as non-decimal numbers. Just make sure the decimals are lined up over one another and that you bring it straight down.

315

0.45

• 0.28_

0.17

Multiplying Decimals
• Get rid of unnecessary zeroes
• Count the number of digits to the right of the decimal in the whole problem
• Ignore the decimal and solve
• Give your answer the same number of digits to the right of the decimal point as the TOTAL number of digits to the right of the decimal in the problem
• Example: 0.25 x 3.80

Get rid of unnecessary zeroes:

0.25 x 3.80  .25 x 3.8

• Count digits:

There are three digits total to the right of the decimal in the problem. (2, 5, and 8)

• Ignore decimals and multiply

1 4

25

x 38

200

+ 75

950

Multiplying Decimals
• Give your answer the same number of digits to the right of the decimal point as the TOTAL number of digits to the right of the decimal in the problem

950

Three digits to the right of the decimal, so:

.950  .95

Multiplying Decimals
• Example 2

6.28 x 2.5

Multiplying Decimals
• Example 2

6.28 x 2.5

There are no zeroes

There are 3 digits to the right of the decimal

628

x 25

3140

1256__

15700  15.700  15.7

Dividing Decimals
• Dividing decimals by whole numbers:
• Simply bring the decimal straight up and then ignore it. Add zeroes to the end of the divisor if necessary to avoid a remainder.
• Example 40.24 ÷ 5
Dividing Decimals
• Non-terminating decimals are decimals that keep going without ever getting to a stopping point. Try dividing 100 by 30.
• The way to show that a decimal doesn’t stop is to draw a line above the decimal digit that continues to repeat. 100 ÷ 30 =
Dividing Decimals By Decimals
• Another Example:

2.604 ÷ 8.4

Do the decimal practice worksheet on page 113 of your book, and check your answers against the answer key posted on BB.

• Do pages 7-10 in the GED Practice Packet, and then fill in the answer sheet on BB to get feedback.