Question

the hcf of two numbers is 3 and their lcm is 36.if one number is 12 what is the other

Answer 1

3 is the hcf, and 36 is the lcm of 12 and x
  therefore x = 6

Answer 2

HCF(a,b) × LCM(a,b) = product of a and b
given one no. is 12
let the other no. be a
HCF(a,12)= 3
LCM(a,12)=36
12×a = 36×3
a= 36×3÷12 = 9