Estimating Decimals

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# Estimating Decimals - PowerPoint PPT Presentation

Estimating Decimals. EQ: How can I use estimation techniques? MA.6.A.3.5. Estimating Decimals. Clustering. What is clustering ?. Clustering. What is clustering ? A method used to estimate a sum or product when all the numbers are close to the same value.

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### Estimating Decimals

EQ: How can I use estimation techniques?

MA.6.A.3.5

Clustering
• What is clustering?
Clustering
• What is clustering?

A method used to estimate a sum or product when all the numbers are close to the same value.

• When would you use clustering to estimate the solution to a problem involving decimals?
Clustering
• What is clustering?

A method used to estimate a sum or product when all the numbers are close to the same value.

• When would you use clustering to estimate the solution to a problem involving decimals?

When all the numbers are close to each other.

Clustering
• Nancy wants to cycle, ice skate, and water ski for 30 minutes each. About how many calories will she burn in all? (Cycling – 165.5 calories, ice skating – 177.5 calories, and water skiing – 171.5 calories.)
• In this example, what number could represent all of the calories?
Clustering
• Nancy wants to cycle, ice skate, and water ski for 30 minutes each. About how many calories will she burn in all? (Cycling – 165.5 calories, ice skating – 177.5 calories, and water skiing – 171.5 calories.)
• In this example, what number could represent all of the calories? 170
Clustering
• Nancy wants to cycle, ice skate, and water ski for 30 minutes each. About how many calories will she burn in all? (Cycling – 165.5 calories, ice skating – 177.5 calories, and water skiing – 171.5 calories.)
• In this example, what number could represent all of the calories? 170
Clustering
• Nancy wants to cycle, ice skate, and water ski for 30 minutes each. About how many calories will she burn in all? (Cycling – 165.5 calories, ice skating – 177.5 calories, and water skiing – 171.5 calories.)
• What operation could you use rather than adding 170 plus 170 plus 170?
Clustering
• Nancy wants to cycle, ice skate, and water ski for 30 minutes each. About how many calories will she burn in all? (Cycling – 165.5 calories, ice skating – 177.5 calories, and water skiing – 171.5 calories.)
• What operation could you use rather than adding 170 plus 170 plus 170?

Multiplication

Rounding
• When rounding a decimal, how do you know which digit to look at?
Rounding
• When rounding a decimal, how do you know which digit to look at?

0. 375

1000

Place a 1 under the decimal and a 0 under each value past the decimal.

Read the whole number and the “spit” number

Rounding
• Explain the rules for rounding a decimal.
Rounding
• Explain the rules for rounding a decimal.
• Underline the specified place value.
Rounding
• Explain the rules for rounding a decimal.
• Underline the specified place value.
• Look to the right of the underlined value.
Rounding
• Explain the rules for rounding a decimal.
• Underline the specified place value.
• Look to the right of the underlined value.
• 5 or more “raise the score” or 4 or less

“let it rest”

Rounding
• If you rounded all the numbers “up”, how would your estimated answer compare to the actual answer to the problem?
Rounding
• If you rounded all the numbers “up”, how would your estimated answer compare to the actual answer to the problem?

If all the numbers were rounded up, the estimated answer would be an

over-estimate

Compatible Numbers
• What are compatiblenumbers?
• Given the expression 33.83 · 1.98, how does the estimated product compare to the actual product? Explain.
• Given the expression 72.77 ÷ 26.14, why would you choose not to round the numbers to 73 and 26?
• What would you use?
Compatible Numbers
• What are compatiblenumbers?

Numbers that are close to the given

numbers that make estimation or

mental math easier.

Compatible Numbers
• Given the expression 33.83 · 1.98, how does the estimated product compare to the actual product? Explain.
Compatible Numbers
• Given the expression 72.77 ÷ 26.14, why would you choose not to round the numbers to 73 and 26?
Compatible Numbers
• Given the expression 72.77 ÷ 26.14, why would you choose not to round the numbers to 73 and 26?
• What would you use?