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3rd grade compatible numbers
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dawn0717
LIF Infant
Member since 5/05 235 total posts
Name:
Kim
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3rd grade compatible numbers
My son is in 3rd grade and I feel dumb asking this but I don't think I am understanding what compatible numbers are.
This is the question:
Which of the following shows estimating 287+491 by using compatible numbers?
A. 100+500 B. 300+400 C. 280+400 D. 280+500
I thought the answer was either 300+500 or 290+490 and neither of those are choices. Help! Thanks!
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Posted 10/2/12 8:50 PM  |
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NAK729
LIF Infant
Member since 9/11 113 total posts
Name:
Nancy
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3rd grade compatible numbers
Compatible numbers are numbers that are close to the actual numbers and easy to add, subtract, multiply, or divide mentally. The answer would be choice D. 280 + 500. You want to keep it close to the actual answer...so basically, if you round 491 up by 9, you want to roung 287 down by 7 so technically you're only 2 off....you don't necessarily have to round the same way. In fact, compatible numbers don't always follow the rounding rules.
Does that make sense??
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| Posted 10/2/12 9:01 PM |
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ladybug8
LIF Adult
Member since 3/07 2660 total posts
Name:
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Re: 3rd grade compatible numbers
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Message edited 10/2/2012 9:12:57 PM.
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| Posted 10/2/12 9:08 PM |
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3rd grade compatible numbers
I heard something about this on a show DS was watching today - don't remember the show though....
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| Posted 10/2/12 9:17 PM |
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dawn0717
LIF Infant
Member since 5/05 235 total posts
Name:
Kim
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3rd grade compatible numbers
Thank you sooo much for your help!!! As you can tell math was never my "thing" lol!
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| Posted 10/2/12 9:18 PM |
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NAK729
LIF Infant
Member since 9/11 113 total posts
Name:
Nancy
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Re: 3rd grade compatible numbers
I"m a HS math teacher so honestly, math is basically my only thing 
If you ever have a math question, please feel free to contact me!
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| Posted 10/2/12 9:23 PM |
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Adri
Joy!
Member since 5/05 3116 total posts
Name:
A
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Re: 3rd grade compatible numbers
Posted by NAK729
I"m a HS math teacher so honestly, math is basically my only thing
If you ever have a math question, please feel free to contact me!
Is this using TERC?
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| Posted 10/3/12 8:51 AM |
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