Question

Find the L.C.M. of the following group of numbers, using

1. the prime factor method and
2. the common division method

14, 21 and 98

Answer 1

L.C.M. of 14, 21 and 98

i. By prime factors
Prime factors of 14 = 2 x 7 = 2¹ x 7¹
Prime factors of 21 = 3 x 7 = 3¹ x 7¹
Prime factors of 98 = 2 x 7 x 7 = 2¹ x 7²
∴ L.C.M. of 14, 21 and 98 = 2¹ x 3¹ x 7² = 294

ii. By common division method

2	14,	21,	98
7	7,	21,	49
	1,	3,	7

∴ L.C.M. of 14, 21 and 98 = 2 x 7 x 3 x 7 = 294