The figure shows that the distance between two points P and

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[GMAT math practice question]

The figure shows that the distance between two points P and Q is 4 cm at the start. Point P moves to the left at the speed of 2.5 cm/sec, and at the same time, Point Q moves to the right at the speed of 2 cm/sec. How many seconds will it take for the distance between P and Q to be 40 cm?

A. 4
B. 6
C. 8
D. 10
E. 12

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by Max@Math Revolution » Sun Oct 13, 2019 5:09 pm
=>

The distance between P and Q after t seconds is 2.5t + 2t + 4 = 4.5t + 4 cm.
Since the same amount of time passes for both of them, we can use the same variable t for time.
Then we have an equation 4.5t + 4 = 40 or 4.5t = 36. So t = 8.

Therefore, C is the answer.
Answer: C

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by Aditi Goyal » Mon Oct 14, 2019 8:14 pm
Dist between P and Q after t seconds is 2.5t + 2t + 4
Dist bw PQ= 4.5t + 4

This implies 4.5t + 4 = 40 or 4.5t = 36.
So t = 8.
Answer - t=8