Estimating to Solve Problems

Lesson 7

Why use estimation?

When solving problems, sometimes an exact answer isn’t needed. Amounts may be rounded and estimation used to calculate a solution.

Place Value

1,234,567,890.123456

What is the value of the 8 in each number?

1,378,12480,123,567321.05378103,21851.81261,085,241.4

How to Round

If the digit following the indicated level of rounding is Less than 5…

5 or greater…

Round to the indicated value.

752 (tens)6,555 (hundreds)752,357 (ten thousands)651.5021 (ones)635 (tens)75,500 (thousands)852.157 (hundredths)65.15 (tenths)

Is it better to over estimate or under estimate?

Ms. Brown has 3 errands to run before a dentist appointment at 10:00 a.m.. To figure out when she should leave her house should she underestimate or overestimate the total time it will take to run these errands?

Is it better to over estimate or under estimate?

Bill wants to buy a new mountain bike which sells for $375. He wants to estimate how long it will take him to save the money he needs based on his weekly earnings from his paper route. Should he underestimate or overestimate his weekly earnings?

Is it better to over estimate or under estimate?

Mary is going to order the fabric for her bridesmaids dresses. Should she underestimate or overestimate the amount she needs for each dress?

On-Line Help

Estimation Practice (Basketball Simulation)Practice ProblemsEstimation GolfEstimator Game for Two (Four Square)

Using Estimation

Josh’s pulse rate was taken at 5 different times. The rates were 92, 88, 87, 86, and 97. What was his average pulse rate?

The scores of 4 students on a recent test were 67, 75, 83, 92, and 100.

Estimate the average score.

AdmissionsThe group of 5 adults and 6 children purchased daily tickets for the Blackpool Zoo. Estimate the total spent on the tickets.

Perimeter and Area

3.87 ft

4.218 ft

Estimate the perimeter of the rectangle to the left.

Estimate the area of the rectangle.

Jogging

Marisol jogged 3.82 miles Monday, 2.15 miles Tuesday, 3.165 miles Wednesday, and 1.52 miles Friday. Estimate the number of miles did Marisol jog that week.