1. Adding Partial Sums

2. First you need to do a Ballpark Estimate
243
+ 208
Ballpark Estimate:___________________________________

3. + 208  estimated to 200 243  estimated to 200
Remember it’s easier to work with estimating when you only have 0s after the first number.
243  estimated to 200
+ 208  estimated to 200
243 is closer to 200 than is it to 300.
Ballpark Estimate:__ =400_________________________

4. Remember how we expand numbers
243 =
+ 208 =
Hundreds
Tens
Ones
Ballpark Estimate:__ =400_________________________

5. Remember how we expand numbers
243 = 200
+ 208 = 200
Hundreds
Tens
Ones
Ballpark Estimate:__ =400_________________________

6. Remember how we expand numbers
243 =
+ 208 =
Hundreds
Tens
Ones
Ballpark Estimate:__ =400_________________________

7. Remember how we expand numbers
243 =
+ 208 =
Hundreds
Tens
Ones
Ballpark Estimate:__ =400_________________________

8. 243 + 208 400 40 11 451 = 200 + 40 + 3 = 200 + 8 Hundreds Tens Ones
Think: = 400 40
Think: = 40 11
Think: = 11
Does my answer make sense? Is it close to my ballpark estimate?
451
YES!
Ballpark Estimate:__ =400_________________________

9. First, make a Ballpark estimate.
Let’s do another one
First, make a Ballpark estimate.
638
+ 429
Ballpark Estimate:___________________________________

10. + 429  estimated to 400 638  estimated to 600
Remember it’s easier to work with estimating when you only have 0s after the first number.
638  estimated to 600
+ 429  estimated to 400
Ballpark Estimate:__ =1,000____________

11. Keep in mind how we expand numbers so we can do partial sums
638 =
+ 429 =
Hundreds
Tens
Ones
Ballpark Estimate:__ =1,000_________________________

12. Hundreds
Tens
Ones
638
+ 429
= 600
+ 30
+ 8
+ 20
+ 9
= 400
1,000
Think: = 1,000 50
Think: = 50 17
Think: = 17
Does my answer make sense? Is it close to my ballpark estimate?
1,067
YES!
Ballpark Estimate:__ =1,000_________________________