Find the LCM and HCF of 12, 15 and 21

Correct option is A

Given:

Numbers: 12, 15, 21 

Solution:

Finding the HCF (Highest Common Factor): 

​$$12: 2^2 \times 3$$ 

15 : $$3 \times 5$$​​

21: 3×7 

The only common factor is 3.

HCF=3

Finding the LCM (Least Common Multiple):

​$$12: 2^2 \times 3$$

15 : $$3 \times 5$$​​

21: 3×7 

LCM = $$2^2 \times 3 \times 5 \times 7$$

LCM = $$4 \times 3 \times 5 \times 7$$

LCM = 4 ×105 

LCM = 420
Thus, correct answer is (a) 420, 3