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Solution:

Step I:Resolving each given number into its prime factors.

16 = 2 × 2 × 2 × 2.

28 = 2 × 2 × 7.

Step II: The product of all the factors with highest powers.

= 2 × 2 × 2 × 2 ×7 = 112.

Step III: The required least common multiple (L.C.M) of 16 and 28 = 112.

LCM by Common Division Method
Step 1: Write the given numbers in a horizontal line, separating them by commas.

Step 2: Divide them by a suitable prime number, which exactly divides at least two of the
given numbers.

Step 3: We put the quotient directly under the numbers in the next row. If the number is not
divided exactly, we bring it down in the next row.

Step 4: We continue the process of step 2 and step 3 until all co-prime numbers are left in the
last row.

Step 5: We multiply all the prime numbers by which we have divided and the co-prime
numbers left in the last row. This product is the least common multiple of the given numbers.

For example: 1. Find least common multiple (L.C.M) of 20 and 30 by division method.

Solution:

Least common multiple (L.C.M) of 20 and 30 = 2 × 2 × 5 × 3 = 60.

Find least common multiple (L.C.M) of 120, 144, 160 and 180 by using division method.