For instance, 2 21 + 1 6 = 4 42 + 7 42 = 11 42 {\displaystyle {2 \over 21}+{1 \over 6}={4 \over 42}+{7 \over 42}={11 \over 42}} where the denominator 42 was used because it is the least common multiple of 21 and 6.
2 21 + 1 6 = 4 42 + 7 42 = 11 42 {\displaystyle {2 \over 21}+{1 \over 6}={4 \over 42}+{7 \over 42}={11 \over 42}} استعمل العدد 42 لأنه هو المضاعف المشترك الأصغر ل 21 و6.