Ex 1.2 , 7
There is a circular path around a sports field. Sonia takes 18 minutes to drive one round of the field, while Ravi takes 12 minutes for the same. Suppose they both start at the same point and at the same time, and go in the same direction. After how many minutes will they meet again at the starting point?
Time taken by Sonia to drive one round = 18 minutes
Time taken by Ravi to drive one round = 12 minutes
Time taken by both to meet again = LCM of 18 & 12
We find LCM of 18 and 12 using prime factorization
L.C.M (Method 1)
L.C.M = Product of greatest power of each prime factor
= 22 × 32
= 4 × 9 = 36
Hence, Time taken by both to meet again
= LCM of 18 & 12 = 36 minutes
L.C.M (Method 1)
L.C.M = 2 × 2 × 3 × 3
= 36
Hence, Time taken by both to meet again
= LCM of 18 & 12 = 36 minutes

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Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths and Science at Teachoo.