Question

The LCM of two numbers is2^2×3×7.The HCF of the same numbers is 2×7.One of the numbers is the number of days in February 2013. What is the other number?

Answer 1

We know that
HCF * LCM = First number * second number
2*2*3*7 * 2*7 = 28 * x
x = 42
Thus, the other number is 42.

Answer 2

LCM = 2²×3×7
HCF = 2×7

One of the number = 28
let other number = x

we know that 
product of LCM and HCF = product of the two numbers
⇒ 2²×3×7×2×7 = 28×x
⇒ x = (2²×3×7×2×7)/28
⇒ x = 42

So other number is 42.