Quick Review

1
Quick Review

• Round to the place value of the underlined digit
• 1. 3, 528
• 2. 131,295
• 3. 229,000
• 4. 995

• Answers
• 3,500
• 130,000
• 200,000
• 1,000

2
Using Estimation Strategies

• Section 1-1 (pages 5-9)

3
Estimate or Exact?

• Suppose you are writing a news article. Your
  notes contain some data that may be estimates.
  For each situation, decide whether you have an
  estimate or an exact value. Explain your
  decision.
• a) The population of Florida is 16,000,000.
• b) Florida has 25 representatives in the U.S.
  House of Representatives.

Estimate
Exact Value
Other examples??
4
Things to Remember

• Estimate a number before you calculate it
• Use the symbol which means
• approximately equal to

5
Estimating a Sum or Difference

• At the zoo, you see a Colombian black spider
  monkey. The length of its body is 58.31 cm. The
  Length of its tail is 78.96 cm. To the nearest
  tenth of a centimeter, estimate the total length
  of the monkeys body and tail.

58.31 78.96 58.3 79.0

• Round to nearest tenth

• Add

137.3 cm
6
Estimating a Product

• A rectangular kitchen is 8.5 ft long and 5.75 ft
  wide. Use rounding to estimate the area of the
  kitchen in square feet.

8.5 9 5.75 6

• Round each factor to the nearest whole number

9 6 54 ft2

• Multiply

7
Extra Practice

• Estimate. Round to the nearest whole number
  before you add or subtract
• 1) 10.13 1.46
• 2) 14.17 - 10.92
• 3) 11.53 7.23
• 4) 9.35 - 0.81

11
3
19
8
8
Extra Practice

• Estimate. Round to the nearest whole number
  before you multiply.
• 1) 4.9 x 12.2
• 2) 6.07 x 3.29
• 3) 7.65 x 5.33
• 4) 25.123 x 4.79

60
18
40
125
9
Estimating by Front-End Estimation

• Useful for finding sums or differences.
• Two Steps
• 1) Add (Subtract) the front numbers
• 2) Estimate the sum of the lesser numbers and
  adjust the estimate

10
Estimating by Front-End Estimation

• Suppose you went food shopping with your parents
  this weekend and bought Lucky Charms for 3.21, a
  frozen pizza for 4.79, Pepsi for 1.99, and a
  pack of gum for 1.15. Estimate the total cost of
  your purchases.

Step 1 Add the front-end digits 3.21
4.79 1.99 1.15 9
Step 2 Estimate the total amount of cents to the
nearest dollar. 3.21
4.79 1.99 1.15
2
About 1
About 1
The total cost is about 11.
11
Extra Practice

• A group of runners run a relay race in which each
  runner decides how long they run for. Their
  distances were 3.9 miles, 2.1 miles, 1.7 miles,
  1.2 miles, and 3.3 miles. Estimate the total
  distance of the race.

Step 1 Add the front-end digits 3.9 2.1
1.7 1.2 3.3 10
Step 2 Estimate the total amount of tenths of a
mile to the nearest mile. 3.9
2.1 1.7 1.2 3.3

2
About 1
About 1
The total distance is about 12 miles.
12
Extra Practice

• Use Front-End Estimation to estimate each sum.
• 1) 5.43 2.67
• 2) 8.09 11.24
• 3) 7.18 5.89
• 4) 3.62 2.31

8
19
13
6
13
What is a compatible number?

• Numbers that are easy to compute mentally. You
  can use compatible numbers to estimate.
• Change the numbers of the problem to make the
  calculation easier.
• Useful for finding quotients.

14
Using Compatible Numbers

• It took 75.75 pounds of shredded cheese to make
  the worlds largest burrito. Use compatible
  numbers to estimate how many 10 pound boxes of
  shredded cheese the cooks needed.

75.75 10
Set up the Quotient
80 10
Choose compatible numbers such as 10 and 80.
15
Extra Practice

• Use compatible numbers to estimate each quotient.
• 1) 76.5 8.8
• 2) 19.45 4.92
• 3) 103.6 9.72
• 4) 32.2 7.56

9
4
10
4