Question

A and B walk around a circular track. They start at 8 am 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 am?

• A. 6
• B. 5
• C. 7
• D. 8

Answer 1

Answer: (C)

7

Answer 2

A does 1 round per 30 minutes
B does 1 round per 20 minutes
How many minutes would it take making a round together:

$\frac{x}{30}+\frac{x}{20}=1$

2x + 3x = 60
5x = 60
x = 12
They meet every 12 minutes.
How many 12 minute periods are there from 8:00 am to 9:30 am
90 minutes, so

$\frac{90}{12}$

Answer is 7 times they cross each other.
So the correct option is (C)