Xiao's teacher asked him to rewrite the sum \(60 + 90\) as the product of the GCF of the two numbers and a sum. Xiao wrote \(3(20 + 30)\). What mistake did Xiao make? How should he have written the sum?
Answer (2)
His answer works ... it gives 150, which is the same as (60 + 90) ... but he didn't deliver exactly what the problem asked for.
It asked for the GCF to be outside the parentheses, and he put '3' there.
'3' is certainly one common factor of 60 and 90, but it's far from being the greatest one.
The GCF of 60 and 90 is actually 30 . So the absolutely positively technically correct response to the instructions in the problem would be 30(2 + 3).
Xiao mistakenly used the common factor 3 instead of the greatest common factor 30. He should have expressed 60 + 90 as 30 ( 2 + 3 ) . This correctly reflects the GCF as a product of a sum.
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