Estimation in Decimal Multiplication & Division Problems

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Achievement Objectives
NA5-3: Understand operations on fractions, decimals, percentages, and integers.
NA5-6: Know and apply standard form, significant figures, rounding, and decimal place value.
Specific Learning Outcomes

Solve multiplication and division problems that involve fractions.

Use rounding to check the answers to multiplication and division problems.

Description of Mathematics

Number Framework Stage 8

Required Resource Materials
Estimating x/➗ Decimals (Material Master 8-17)
Activity

Using Number Properties

Problem: “Estimate 0.503 x 58.7.”

Discuss why ½ x 60 = 30 is sensible.

Problem: “Martha gets 34.56 ÷ 0.98 = 33.8688 on her calculator. Is she correct?”

(Answer: Martha must be wrong as division by a number less than 1 makes the  answer bigger.)

Problem: “Estimate 59.89 x 0.091.” (Possible answer: 59.89 x 0.091 60 x 0.1, and 1 tenth of 60 = 6.)

Examples: Worksheet (Material Master 8–17).

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Level Five