A lake has a circumference of two kilometers. A and B both d

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[GMAT math practice question]

A lake has a circumference of two kilometers. A and B both departed from the same point on the circumference at the same time and walked in opposite directions. They met 30 minutes after their departure. What is the sum of the speeds of A and B?

A. 3 km/hr
B. 4 km/hr
C. 5 km/hr
D. 6 km/hr
E. 7 km/hr
Source: — Problem Solving |

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by Max@Math Revolution » Sun Aug 18, 2019 5:14 pm
=>

Let a and b be the velocities of A and B, respectively.
Then (30/60)a + (30/60)b = (1/2)a + (1/2)b = 2.
Thus, a + b = 4.

Therefore, B is the answer.
Answer: B