The HCF and LCM of two numbers are 21 and 84 respectively. If the ratio of the two numbers is 1 : 4 then larger of the two numbers is = ?

Answer: Option C

We know,
LCM × HCF = 1^st number × 2^nd number
Let 1^st number = K
2^nd number = 4K
K × 4K = 21 × 84
K = 21
Then number = 21, 84
So, larger number = 84