ABSTRACT
Step 1: the LCM of the two denominators; Step 2: for the fraction 13 , 3 into 21 goes 7 times,
7 × the numerator is 7 × 1; Step 3: for the fraction 27 , 7 into 21 goes 3 times,
3 × the numerator is 3 × 2. Thus
1 3
+ 2 7
= 7 + 6 21
= 13 21
as obtained previously.
