MR K.
asked • 07/29/18A - B = 2255; A - C = 1750; C - B = ? How to teach this concept to kids...
A - B = 2255; A - C = 1750; C - B = ?
How to teach this concept to kids...
Book says answer is 2250 - 1750. But not sure how to teach this to kids..
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1 Expert Answer
Anita A. answered • 07/29/18
Tutor
4.9
(231)
Community College Math Instr; TX Secondary Mathematics Certification
Equals subtracted from equals result in equals.
A + B = 2255
-(A + C) = -1750
A + B = 2255
-A + -C = -1750
B - C = 2255 - 1750 = 505
Either the original problem or the answer key has a misprint.
A2
David W.
To reinforce the concept that equals plus equals results in equals and that equals minus equals results in equals, work it backwards:
What is B - C ?
B - C + 0 [note: The Additive Identity may be added to any number without changing it.]
B - C + (A - A) [because A - A = 0]
B - C + A - A
A + B - A - C [Commutative Property]
(A + B) - (A + C) [Associative Property]
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07/29/18
MR K.
Error in my question. Corrected now. Thanks
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07/29/18
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MR K.
07/29/18