Question

A and B walk around a circular track. They start at 9 a.m. from the same point in the opposite directions. A and B walk at a speed of 2 rounds per hour and 3 rounds per hour respectively. How many times shall they cross each other before 9.30 a.m.?

Answer 1

GIVEN ;-

⇒ A and B walk around the circular track

⇒ A and B starts to walk around the circular park but in opposite direction      
    
                                                                         =  9 a. m

⇒ A and B walk in the speed = 2 rounds/ hr and 3 rounds / hr


TO FIND ;-

⇒How many times shall they cross each other before 9.30 a.m.?


SOL ;-

⇒ Let us find their respective speed. -

Respective speed = Total speed of A + Total speed of B

                           =   2  +  3  = 5

So respective speed or  relative speed is equal to 5 rounds \ hr.

⇒ So by this statement we derive that A and B cross 5 times.

⇒
 Hence we can say that A And B cross 5 times in only 1 hr.

       
                                    A and B cross 2 times in 1 \ 2 hrs


Time lapse  between  8 a.m and 9.30 a.m is  1.5 hrs.




No. of times did A and B cross in 1  hr + No. of times did A and B cross in 1 \2 hrs =   

⇒ 5  +  2 = 7  hrs

⇒Answer ;-  Hence A and B cross 7 times