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Adding Partial Sums

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**First you need to do a Ballpark Estimate**

243 + 208 Ballpark Estimate:___________________________________

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**+ 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_________________________

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**Remember how we expand numbers**

243 = + 208 = Hundreds Tens Ones Ballpark Estimate:__ =400_________________________

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**Remember how we expand numbers**

243 = 200 + 208 = 200 Hundreds Tens Ones Ballpark Estimate:__ =400_________________________

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**Remember how we expand numbers**

243 = + 208 = Hundreds Tens Ones Ballpark Estimate:__ =400_________________________

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**Remember how we expand numbers**

243 = + 208 = Hundreds Tens Ones Ballpark Estimate:__ =400_________________________

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**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_________________________

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**First, make a Ballpark estimate.**

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

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**+ 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____________

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

638 = + 429 = Hundreds Tens Ones Ballpark Estimate:__ =1,000_________________________

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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_________________________

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