sir
 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?
 
sir for this sum why we should not find hcf
 

Asked by seeni2005 | 8th Jul, 2016, 06:56: PM

Expert Answer:

begin mathsize 16px style The space time space at space which space Ravi space and space Sonia space will space meet space at space the space starting space point
equals space LCM space of space the space time space taken space by space Ravi space and space Sonia space to space complete space 1 space round space of space the space circular space path
equals LCM space of space 18 space and space 12 end style
begin mathsize 16px style LCM space straight o space straight f 18 space and space 12 space equals space 2 cross times 3 cross times 3 cross times 2 equals 36
That space is space after space 36 space minutes space both space will space meet space at space the space starting space point.
Now comma space Ravi space takes space lesser space time space than space Sonia space to space complete space 1 space round.
This space means space only space after space Ravi space completes space 1 space round comma space they space will space meet space at space the space starting space point.
The space HCF space of space 18 space and space 12 space will space be space less space than space or space equal space to space 18 space and space 12 comma
this space means space it space is space surely space not space possible space for space Ravi space and space Sonia space to space meet space at space the space starting space point space at space straight a space time space less space than space the space time space
taken space by space them space to space complete space 1 space round. end style
So, the HCF does not help in finding the time at which they will meet at the starting point.

Answered by Rebecca Fernandes | 10th Jul, 2016, 08:40: PM