1. 4.2 Estimating Sums & Differences

2. What are some things that are often rounded?

3. Target
We will use rounding to estimate sums and differences.

4. Rounding Review! 5 or more, add one more! 4 or less, stay! 1,325 300
350
400

5. Vera went on a 3-day trip in which she traveled 336 miles the first day, 423 miles the second day, and 357 miles on the third day. Is 300 or 400 a more reasonable estimate for about how far she went on each of the days?

6. Rounded to Nearest Hundred
Vera went on a 3-day trip in which she traveled 336 miles the first day, 423 miles the second day, and 357 miles on the third day.
Vera’s Distances
Miles Traveled
Rounded to Nearest Hundred
1st day
2nd day
3rd day

7. When would you want to use an estimate instead of an exact answer?
When you need to decide how many packages to buy when items are sold in certain quantities.

8. The Empire State Building was completed in 1931
The Empire State Building was completed in From ground to tip it measures 1,250. At the top of the building is a lightening rod which measures 204 feet. Estimate the total height of the building.
Is the answer reasonable?

9. 1. Write the numbers vertically (up and down). 2
1. Write the numbers vertically (up and down) Decide which place to round to. Round each number Add or subtract the rounded numbers Check your answer for reasonableness.

10. The Washington Monument was completed in 1884
The Washington Monument was completed in About how many years after was the Empire State Building completed? 10

11. This is not reasonable!!
How would rounding the dates to the nearest hundreds change the usefulness of the estimate?

12. You Try!
Compare the years Illinois (1818) and Wyoming (1890) acquired statehood.

13. You Try!
5 6 3

14. You Try!
2 8 8

15. You Try!

16. You Try!

17. You Try!

18. You Try!

19. 1. What are we studying today. 2. What did we learn. 3
1. What are we studying today? What did we learn? What are the steps?

20. 1. Write the numbers vertically (up and down). 2
1. Write the numbers vertically (up and down) Decide which place to round to. Round each number Add or subtract the rounded numbers Check your answer for reasonableness. Pg 94 - #9-12, 17, 18, 23, 24, 27, 29 CHALLENGE: Pg. 95 # 25