Adding Partial SumsAdding Partial Sums

First you need to do a Ballpark Estimate

243243

+ 208+ 208

Ballpark Estimate:___________________________________

Remember it’s easier to work with estimating Remember it’s easier to work with estimating when you only have 0s after the first number.when you only have 0s after the first number.

243 243 estimated to estimated to 220000

+ 208 + 208 estimated to estimated to 220000

243 is closer to 200 than is it to 300.

Ballpark Estimate:__200+200=400_________________________

Remember how we expand Remember how we expand numbersnumbers

224433 = = 200 200 + + 40 40 + + 33

+ + 220088 = = 200 200 + + 00 + + 88

Ballpark Estimate:__200+200=400_________________________

Hundr

eds

Tens

Ones

Remember how we expand Remember how we expand numbersnumbers

224433 = = 200200

+ + 220088 = = 200200

Ballpark Estimate:__200+200=400_________________________

Hundr

eds

Tens

Ones

Remember how we expand Remember how we expand numbersnumbers

224433 = = 200 200 + + 4040

+ + 220088 = = 200 200 + + 00

Ballpark Estimate:__200+200=400_________________________

Hundr

eds

Tens

Ones

Remember how we expand Remember how we expand numbersnumbers

224433 = = 200 200 + + 40 40 + + 33

+ + 220088 = = 200 200 + + 00 + + 88

Ballpark Estimate:__200+200=400_________________________

Hundr

eds

Tens

Ones

224433 + + 220088

Ballpark Estimate:__200+200=400_________________________

Hundr

eds

Tens

Ones

= = 200200

+ + 4040

+ + 33

= = 200200

+ + 88

Think: Think: 200200 + + 200200 = = 400400400400

Think: Think: 4040 + + 00 = = 40404040Think: Think: 33 + + 88 = = 11111111

445511

Does my answer make sense? Is it close to my ballpark estimate?

YES!

First, make a First, make a Ballpark estimate.Ballpark estimate.

638638

+ 429+ 429

Ballpark Estimate:___________________________________

Let’s do another oneLet’s do another one

Remember it’s easier to work with estimating Remember it’s easier to work with estimating when you only have 0s after the first number.when you only have 0s after the first number.

638 638 estimated to estimated to 660000

+ 429 + 429 estimated to estimated to 440000

Ballpark Estimate:__600+400=1,000____________

Keep in mind how we expand numbers Keep in mind how we expand numbers so we can do partial sumsso we can do partial sums

663388 = = 600 600 + + 30 30 + + 88

+ + 442299 = = 400 400 + + 2020 + 9 + 9

Ballpark Estimate:__600+400=1,000_________________________

Hundr

eds

Tens

Ones

663388 + + 442299

Ballpark Estimate:__600+400=1,000_________________________

Hundr

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Ones

= = 600600

+ + 3030

+ + 88

= = 400400

+ + 99

Think: Think: 600600 + + 400400 = = 1,0001,0001,0001,000Think: Think: 3030 + + 2020 = = 50505050

Think: Think: 88 + + 99 = = 171717171,1,006677

+ + 2020

Does my answer make sense? Is it close to my ballpark estimate?

YES!