How to solve m/3n + 2/7n

Algebra
Tutor: None Selected Time limit: 1 Day

How to solve m/3n + 2/7n , I know the answer is 7n+6/21n but How did you get there? the app im using only says "cross multiply" to which iam getting 7nm+6n/21n^2.

Dec 10th, 2014

For this one you have to first find the least common denominator:

each denominator factors as follows

(3)(n) and (7)(n)

so they already have n in common, but because 7 and 3 cannot be further broken down, 

they are multiplied to form 21, ......so (21)(n) is your least common denominator

then you have to multiply the fraction on the left by (7)/(7) and the fraction on the right by (3)(3), which would give you the right answer
. multiplying by 1 does not change the value of 

each fraction but gets them into terms where you can add. You can't cross multiply with 
addition of fractions
Dec 10th, 2014

Thanks

Sep 3rd, 2015

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Dec 10th, 2014
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Dec 10th, 2014
Dec 9th, 2016
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