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

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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.

Oct 21st, 2017

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, (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


Sep 3rd, 2015

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Oct 21st, 2017
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