A,B are start walking around a Circular park of radius 70m. They start at the same point, and A goes clockwise at 10m/s, while b goes anti-clockwise at 20m/s.How many times will they cross each other at the starting point if they walk for 30 minutes?
a) 20
b) 40
c) 60
d) 80
e) None of the above

1 Answer

Answer :

Radius = 70m, So circumference = 2 × (22/7) × 70 =440m
Relative speed = 10 +20 = 30m/s
They will meet everytime at the starting point when the distance covered by both put
together is a multiple of 440
LCM of (440,30) = 44 × 30
So, they will meet at starting point every 44 seconds.
In 30minutes, they will meet =1800/44 =40.9
So they will meet 40 times (we need to ignore the decimal part).
Answer : b

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