Question

Find the LCM and HCF of 12, 15 and 21 by applying the prime factorization method. [2 MARKS]

Answer 1

Prime factorisation : 1 Mark
H.C.F : 0.5 Mark
L.C.M : 0.5 Mark

$$\begin{array}{cc}2& 12\\ 2& 6\\ & 3\end{array}$$

12 = 2$\times$2$\times$3

$$\begin{array}{cc}3& 15\\ & 5\end{array}$$

15 = 3$\times$5

$$\begin{array}{cc}3& 21\\ & 7\end{array}$$

21 = 3$\times$7

So H.C.F = 3

L.C.M = 420