1-1 Homework Answers

Agenda: 6th Gr Math: 1-2 HW

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1-2 Estimating with Whole Numbers

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Warm UpWarm Up

Lesson PresentationLesson Presentation

Problem of the DayProblem of the Day

Warm UpFind each sum.

1. 3,214 + 5,490

2. 9,225 + 8,652

3. 3,210 + 1,200

4. 8,774 + 2,156

8,704

17,877

4,410

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1-2 Estimating with Whole Numbers

10,930

Problem of the Day

Continue the number pattern below. Explain the pattern you found.3, 6, 10, 15, ___, ___

21, 28; One possible pattern is to increase the difference between consecutive terms by one more than the difference between preceding consecutive terms.

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1-2 Estimating with Whole Numbers

Learn to estimate with whole numbers.

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1-2 Estimating with Whole Numbers

Vocabulary

compatible numberunderestimateoverestimate

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1-2 Estimating with Whole Numbers

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1-2 Estimating with Whole Numbers

Sometimes in math you do not need an exact answer. Instead, you can use an estimate. Estimates are close to the exact answer but are usually easier and faster to find.

When estimating, you can round the numbers in the problem to compatible numbers. Compatible numbers are close to the numbers in the problem, and they can help you do math mentally.

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1-2 Estimating with Whole Numbers

When rounding, look at the digit to the right of the place to which you are rounding.

• If that digit is 5 or greater, round up.

• If that digit is 4 or less, stay put!

Remember!

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1-2 Estimating with Whole Numbers

Additional Example 1A: Estimating a Sum or Difference by Rounding

Estimate the sum by rounding to the place value indicated.

A. 12,345 + 62,167;

ten thousands

10,000 Round 12,345 down.

Round 62,167 down.+ 60,000__________

The sum is about 70,000.

70,000

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1-2 Estimating with Whole Numbers

Additional Example 1B: Estimating a Sum or Difference by Rounding

Estimate the difference by rounding to the place value indicated.

B. 4,983 – 2,447;

thousands

5,000 Round 4,983 up.

Round 2,447 down. – 2,000__________

The difference is about 3,000.

3,000

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1-2 Estimating with Whole Numbers

Try This: Example 1A

Estimate the sum by rounding to the place value indicated.

A. 13,235 + 41,139;

ten thousands

10,000 Round 13,235 down.

Round 41,139 down.+ 40,000__________

The sum is about 50,000.

50,000

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1-2 Estimating with Whole Numbers

Try This: Example 1B

Estimate the difference by rounding to the place value indicated.

B. 5,723 – 1,393;

thousands

6,000 Round 5,723 up.

Round 1,393 down. – 1,000__________

The difference is about 5,000.

5,000

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1-2 Estimating with Whole Numbers

An estimate that is less than the exact answer is an underestimate.

An estimate that is greater than the exact answer is an overestimate.

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1-2 Estimating with Whole Numbers

The area of a rectangle is found by multiplying the length by the width.

A = l w

l

w

Remember!

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1-2 Estimating with Whole Numbers

Additional Example 2: Estimating a Product by Rounding

The sixth-grade class wants to paint a wall with white paint. The wall is a rectangle 9 feet tall and 18 feet wide. One quart of paint will cover 100 square feet. How many quarts of paint should the students buy?

9 18 9 20 Overestimate the area of the wall.

The actual area is less than 180 square feet.

9 20 = 180

If one quart of paint will cover 100 square feet, then 2 quarts will cover 200 square feet. The students should buy 2 quarts of paint.

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1-2 Estimating with Whole Numbers

Try This: Example 2

The seventh-grade class wants to paint a wall with blue paint. The wall is a rectangle 9 feet tall and 29 feet wide. One quart of paint will cover 100 square feet. How many quarts of paint should the students buy?

9 29 9 30 Overestimate the area of the wall.

The actual area is less than 270 square feet.

9 30 = 270

If one quart of paint will cover 100 square feet, then 3 quarts will cover 300 square feet. The students should buy 3 quarts of paint.

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1-2 Estimating with Whole Numbers

Additional Example 3: Estimating a Quotient Using Compatible Numbers

Mr. Dehmel will drive 243 miles to the fair at 65 mi/h. About how long will his trip take?

243 ÷ 65 240 ÷ 60240 and 60 are compatible numbers. Underestimate the speed.

Because he underestimated the speed, the actual time will be less than 4 hours..

240 ÷ 60 = 4

The trip will take about 4 hours.

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1-2 Estimating with Whole Numbers

Try This: Example 3

Mrs. Blair will drive 103 miles to the airport at 55 mi/h. About how long will her trip take?

103 ÷ 55 100 ÷ 50100 and 50 are compatible numbers. Underestimate the speed.

Because she underestimated the speed, the actual time will be less than 2 hours..

100 ÷ 50 = 2

The trip will take about 2 hours.

Lesson Quiz

Estimate each sum or difference by rounding to the place value indicated.

1. 7,420 + 3,527; thousands

2. 47,821 + 19,925; ten thousands

3. 8,254 – 5,703; thousands

4. 66,845 – 24,782; ten thousands

5. One quart of paint covers an area of 100 square

feet. How many quarts are needed to paint a wall 8

feet tall and 19 feet wide?

70,000

11,000

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2,000

50,000

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1-2 Estimating with Whole Numbers

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