1-1 Estimating with Whole Numbers Warm Up Warm Up Lesson Presentation Lesson Presentation Problem of the Day Problem of the Day Lesson Quizzes Lesson Quizzes

1-1 Estimating with Whole Numbers

Warm UpWarm Up

Lesson PresentationLesson Presentation

Problem of the DayProblem of the Day

Lesson Quizzes


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

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.


Learn to estimate with whole numbers.


Vocabulary

estimate

compatible numberunderestimateoverestimate


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.


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 less than 5, round down.

Remember!


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

Estimate the sum by rounding to the place value indicated.

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


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

Estimate the difference by rounding to the place value indicated.

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


Check It Out: Example 1A

Estimate the sum by rounding to the place value indicated.


10,000 Round 13,235 down.

Round 41,139 down.+ 40,000__________

The sum is about 50,000.

50,000


Check It Out: Example 1B

Estimate the difference by rounding to the place value indicated.

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


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

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


Additional Example 2: Estimating a Product by Rounding

Chelsea is planning the annual softball banquet for the 8 teams in the region. Each team has 18 members. Estimate how many plates she will need to buy if all the members attend.

8 18 8 20 Overestimate the number of softball members.

The actual number of softball members is less than 160.

8 20 = 160

Chelsea should buy about 160 plates.

Find the number of softball members.


Additional Example 2 Continued

Another method

8 18 10 18 Overestimate the number of teams.

The actual number of softball members is less than 180.

10 18 = 180

Chelsea should buy about 180 plates.

Find the number of softball members.


Check It Out: Example 2

Ms. Oliver wants to buy the entire seventh-grade new pencils. There are 5 seventh-grade homeroom classes of 28 students. Estimate how many pencils Ms. Oliver needs to buy for all of the students.

5 28 5 30 Overestimate the number of students.

The actual number of students is less than 150.

5 30 = 150

Ms. Oliver should buy about 150 pencils.

Find the number of students in the seventh grade.


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.


Check It Out: 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.


Standard Lesson Quiz

Lesson Quizzes

Lesson Quiz for Student Response Systems


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

2,000

50,000

2


1. Estimate by rounding to the indicated place value.

8,240 + 3,428; thousands

A. 10,000

B. 11,000

C. 12,000

D. 13,000





A. 60,000

B. 70,000

C. 80,000

D. 90,000




7820 – 4860; thousands

A. 1,000

B. 2,000

C. 3,000

D. 4,000




55,726 – 25,832; ten thousands

A. 50,000

B. 40,000

C. 30,000

D. 20,000



5. One gallon of floor polish is required to polish an area of 50 square feet. How many gallons are required to polish a floor 9 feet long and 11 feet wide?

A. 1 gallon

B. 2 gallons

C. 3 gallons

D. 4 gallons


Documents

1-1 Estimating with Whole Numbers Warm Up Warm Up Lesson Presentation Lesson Presentation Problem of the Day Problem of the Day Lesson Quizzes Lesson Quizzes