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.