EXAMPLE 1 Biking The map shows biking times for a trail. Estimating Sums and Differences

EXAMPLE 1

Biking The map shows biking times for a trail.

Estimating Sums and Differences

EXAMPLE 1

Biking The map shows biking times for a trail.

a. Estimate how long it takes to bike from the trailhead to the swinging bridge and then to the waterfall.

Estimating Sums and Differences

EXAMPLE 1

Biking The map shows biking times for a trail.

a. Estimate how long it takes to bike from the trailhead to the swinging bridge and then to the waterfall.

b. The biking time from the swinging bridge, past the waterfall, to the trailhead is 208 minutes. Estimate the number of minutes it takes to bike from the waterfall to the trailhead.

Estimating Sums and Differences

EXAMPLE 1

SOLUTION

a. Round the two times to the same place value. Then add.

Estimating Sums and Differences

EXAMPLE 1

SOLUTION

a. Round the two times to the same place value. Then add.

28+ 114

Estimating Sums and Differences

EXAMPLE 1

SOLUTION

a. Round the two times to the same place value. Then add.

28+ 114

Round each number to the nearest ten.

Estimating Sums and Differences

EXAMPLE 1

SOLUTION

a. Round the two times to the same place value. Then add.

28+ 114

Round each number to the nearest ten.

30110

Round 28 up to 30.

Round 114 down to 110.+

Estimating Sums and Differences

EXAMPLE 1

SOLUTION

a. Round the two times to the same place value. Then add.

28+ 114

Round each number to the nearest ten.

30+ 110

140

Estimating Sums and Differences

Round 28 up to 30.

Round 114 down to 110.

EXAMPLE 1

SOLUTION

a. Round the two times to the same place value. Then add.

28 Round each number to the nearest ten.

ANSWER: It takes about 140 minutes to bike from the trailhead to the swinging bridge and then to the waterfall.

Estimating Sums and Differences

+ 11430

+ 110

140

Round 28 up to 30.

Round 114 down to 110.

EXAMPLE 1

208- 114

b.

Estimating Sums and Differences

EXAMPLE 1

208- 114

Round each number to the nearest hundred.

b.

Estimating Sums and Differences

EXAMPLE 1

208- 114

Round each number to the nearest hundred.

200- 100

Round 208 down to 200.

Round 114 down to 100.

b.

Estimating Sums and Differences

EXAMPLE 1

208- 114

Round each number to the nearest hundred.

b.

200- 100

100

Estimating Sums and Differences

Round 208 down to 200.

Round 114 down to 100.

EXAMPLE 1

Round each number to the nearest hundred.

ANSWER: It takes about 100 minutes to bike from the waterfall to the trailhead.

b.

208- 114

200- 100

100

Estimating Sums and Differences

Round 208 down to 200.

Round 114 down to 100.

GUIDED PRACTICE for Example 1

Estimate the sum or difference.

27 641.

GUIDED PRACTICE

Estimate the sum or difference.

1.

ANSWER 90

for Example 1

27 641.

GUIDED PRACTICE

Estimate the sum or difference.

180 9142.

for Example 1

GUIDED PRACTICE

Estimate the sum or difference.

2.

for Example 1

180 9142.

ANSWER 1100

GUIDED PRACTICE

Estimate the sum or difference.

91 493.

for Example 1

GUIDED PRACTICE

Estimate the sum or difference.

3.

ANSWER 40

for Example 1

91 493.

GUIDED PRACTICE

Estimate the sum or difference.

612 834.

for Example 1

GUIDED PRACTICE

Estimate the sum or difference.

4.

ANSWER 530

for Example 1

612 834.