Three elephents A, B and C are moving along a straight line with constant speed in same direction as shown in figure. Speed of A is `5 m//s` and speed of C is `10 m//s`. Initially separation between A & B is 'd' and between B & C is also d. when 'B' catches 'C' separation between A & C becomes 3d. then the speed of B will be

Options

A. ` 7.5 m//s`
B. ` 15 m//s `
C. ` 20 m//s`
D. ` 5m//s`

Answer

B

Explanation

Let speed of B be v.Time taken by B to catch ` c= (d)/(v-10) `
After this time , separation between A and C is 3d ` " "rArr 2d + (10 -5) (d)/(v-10) =3d rArr v=15 m//s `