1. Estimating Sums and Differences

2. Estimating Sums and Differences
Estimating sums and differences can be achieved by rounding the same place value in all numbers.

3. How do you do it?
You can estimate sums and differences by rounding ALL NUMBERS TO THE LARGEST PLACE VALUE OF THE SMALLEST NUMBER.
786 = 790
+ 52 = + 50
840
23,485 = 23,000
- 9,357 = - 9,000
14,000

4. How do you ESTIMATE decimal sums and differences?
When estimating decimals, sums and differences are rounded the same as whole numbers. ALL NUMBERS ARE ROUNDED TO THE LARGEST PLACE VALUE OF THE SMALLEST NUMBER. = =
2.5
- 0.3
2.2 = =
7.4
+ 0.9
8.3

5. Now you try!
Estimate
1) 8.36 2)
- 7.94 3)
+ 6.2

6. How Did You Do?

7. Warm-Up Write the answer you got on #2, 4, 6 p.710 in word form.
Example: 0.8 > 0.67
eight tenths is greater than
sixty-seven hundredths

8. Multiplication Estimation
When multiplying, Always round to the highest place value of each number!!! DO NOT round single digits!
Always drop the decimal point and the zeroes after the decimal!!!

9. Dracula Decimal Lane 18.7 7 Each house needs 18.7 bags of candy.
There are 7 houses that need candy. 7
How many bags of candy does he need?

10. 20
18.7 .0 7 7 x
140

11. Let's Practice, Pumpkins!
157.09
200
25.98
X 15 30
.00 20
X 33.57 x 30 x
6,000
600

12. Division Estimation
When dividing, Always round to division friendly numbers!!! DO NOT round single digits!
Always drop the decimal point and the zeroes after the decimal!!!

13. Dracula Decimal Lane
The neighborhood needs pieces of candy.
302.8
Each house gets about 48.2 pieces of candy to hand out.
48.2
About how many houses are in the neighborhood?

14. 302.8
48.2 = 6 50 .0
300 .0

15. 23.8
82.5 7 21 3 20 80 4 = =