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### Estimating for Reasonableness

• Estimation is used when an exact answer is not needed.
• Most estimation techniques involve replacing numbers and with ones that are close and easy to compute mentally.
• Compatible numbers do not always follow the rules of estimating. For example, 310 ÷ 65 by using compatible numbers is 300 ÷ 60 = 5 compared to estimating which would be 300 ÷ 70.

## Estimate 273 ÷ 28 using compatible numbers.

• 273 is close to 270.28 is close to 30.
• 270 ÷ 30 =

## Estimate 37 × 3 using compatible numbers.

• 37 is close to 40.
• 40 × 3 =

## Estimate 694.3 - 125.5 to the nearest ones place.

• 694.3 rounds to 694
• 125.5 rounds to 126
• 694 - 126 =

## Estimate 1,927.5638 + 52,934.56 to the nearest hundreds place.

• 1,927.5638 rounds to 1,930.
• 52,934.56 rounds to 52,930
• 1,930 + 52,930 =

## Estimate 56.783 - 5.477 to the nearest hundredths place.

• 56.783 rounds to 56.78.
• 5.477 rounds to 5.48.
• 56.78 - 5.48 =

## What is 129 × 52 using compatible numbers?

• 129 is close to 130
• 52 is close to 50.
• 130 × 50 =

## You go out to eat and order a salad for \$ 4.95, soup for \$ 3.65, and steak for \$ 11.99. What is the estimated total cost of your meal?

• \$ 4.95 is close to \$ 5
• \$ 3.65 is close to \$ 3.50
• \$ 11.99 is close to \$ 12
• \$ 5 + \$ 3.50 + \$ 12 =

## Margaret is saving money to buy a new jacket that costs \$ 29.78. She has already saved \$ 12.43. Around how much more money does she still need to save buy the jacket?

• The word Around tells us we need to estimate the amount
• \$ 29.78 - \$ 12.43 = the exact amount of money Margaret still needs
• \$ 29.78 rounds to \$ 29.75
• \$ 12.43 rounds to \$ 12.45
• \$ 29.75 - \$ 12.45 = the estimated amount of money Margaret still needs

## You buy shoes for \$ 14.56, socks for \$ 3.21, and pants for \$ 29.07. The total comes to \$ 46.84. Is this reasonable?

• \$ 14.56 rounds to \$ 14.60
• \$ 3.21 rounds to \$ 3.20
• \$ 29.07 rounds to \$ 29.10
• \$ 14.60 + \$ 3.20 + \$ 29.10 =
• \$ 46.90, which is indeed close to the total of \$ 46.85

## Derrick buys a book for \$ 10.92, a backpack for \$ 37.89, and a calculator for \$ 12.53. The total comes to \$ 80.34. Is this reasonable?

• \$ 10.92 rounds to \$ 11
• \$ 37.89 rounds to \$ 38
• \$ 12.53 rounds to \$ 12.50
• \$ 11 + \$ 38 + \$ 12.50 =
• \$ 61.50, which is not close to the total of \$ 80.34

### No

*These practice questions are only helpful when you work on them offline on a piece of paper and then use the solution steps function to check your answer.