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?
It is a question on how to find the LCM (Lowest Common Multiple) of the two numbers 12 and 18. You might be able to guess that the LCM is 36 , that is (12 x 3) and (18 x 2 ) both equal 36, or in other words Sonia drives around 2 times in 36 minutes and Ravi drives around 3 times in 36 minutes before they are both exactly at the same place on the circular track again.
Or you could try this type of analysis involving identifying the factors of the numbers:
12 = 2 x 2 x 3 ( thats's 2 squared times 3 )
18 = 2 x 3 x3 ( that's 2 times 3 squared )
The lowest number that is a multiple of 2 and 2 squared is 2 squared
The lowest number that is a multiple of 3 and 3 squared is 3 squared
So the lowest common multiple of both expressions is
2 squared times 3 squared = 36