Math CentralQuandaries & Queries


Question from Nick, a student:

Hi i would like to thank penny for helping me last time and need more assistance. It would seem I understand you better then my teacher
anyhow, it asks me to combine fractions i tried cross multiplying and it just doesn't work.

2m/t + 5/mt

Hi Nick,

Thanks for the compliment.

You need to find a common denominator as you would in adding 2/3 and 5/6. In this numeric case if you multiply the numerator and denominator of 2/3 by 3 you get

2/3 = (2 × 2)/(2 × 3) = 4/6.


2/3 + 5/6 = 4/6 + 5/6 = (4 + 5)/6 = 9/6 = 3/2.

In your algebraic expression

2m/t + 5/mt

Multiplying the numerator and denominator of the first fraction by m gives a common denominator to the two fractions which then allows you to combine them.

I hope this helps,

About Math Central


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.
Quandaries & Queries page Home page University of Regina PIMS