How do you evaluate #\frac { 3} { 8} + \frac { 5} { 7} #?

1 Answer
Mar 2, 2018

We find a common multiple of both denominators and then add them.

Explanation:

The two denominators are 7 and 8. We want to find the lowest common multiple of these numbers. In this case, we just multiply them together.
#7xx8=56# which is the lowest common multiple. Then we need to multiply both numerators by the opposite denominators and divide them by the lowest common multiple. Algebraically, this looks like
#frac{a}{b}+frac{c}{d}=frac{ad+bc}{bd}#
For this equation, it looks like #frac{3}{8}+frac{5}{7}=frac{3xx7+5xx8}{7xx8}=frac{21+40}{56}=frac{61}{56}#