Find out primes of each denominator:
Add 1/15 and 7/10
Solution:
Step 1: Find out primes of each denominator.
15 = 5 x 3
10 = 5 x 2
Step 2: In the given example, 15 is the largest denominator, so use the 5 and the 3; now look at the second denominator's primes-here the five already appears in the list, but the 2 does not, so use the 2.
5 x 3 x 2 = 30
Step 3: Rewrite with least general denominators.
1/15 = 2/30
7/10 = 21/30
Step 4: Add the new fractions.
2/30 + 21/30 = 23/30