Find the L.C.M of the following numbers: 

(a) 9 and 4

(b) 12 and 5

(c) 6 and 5

(d) 15 and 4

Observe a common property in the obtained L.C.Ms. Is L.C.M. the product of two numbers in each case?

The least common multiple of two or more numbers is the smallest number among all common multiples of the given numbers.

Answer: LCM is the product of two numbers if they are co-prime. 

Let's find the LCM of the given numbers.

Explanation: 

We know that LCM is the product of two numbers if they are co-prime. 

Hence, 

(a) 9 and 4 - co-prime numbers.

Hence, LCM = 9 x 4 = 36

(b) 12 and 5 - co-prime numbers.

Hence, LCM = 12 x 5 = 60

(c) 6 and 5 - co-prime numbers.

Hence, LCM = 6 x 5 = 30

(d) 15 and 4 - co-prime numbers.

Hence, LCM = 15 x 4 = 60

Thus, LCM is the product of two numbers if they are co-prime.