Gmat1008 wrote:

A frog is climbing a greasy pole. The frog can climb 2 centimeters every half-hour and it takes a break to rest for half an hour after every 2 hours, during which it slips by 1 centimeter. How much time it will take to climb a 28 centimeter pole?

1) 7.5 hours

2) 8.5 hours

3) 9.25 hours

4) 9.75 hours

5) 10 hours

In 2.5 hours, the frog can climb a total of 8 centimeters but will slip back 1 centimeter; thus, it will have covered a distance of 7 centimeters. We need to be careful not to just conclude that it will take 2.5 x 4 = 10 hours, because once the frog reaches the top, it will not rest and slip back again. Instead, we proceed as follows:

In 7.5 hours, the frog will be 21 centimeters high.

In 8 hours, the frog will be at 23 centimeters.

In 8.5 hours, the frog will be at 25 centimeters.

In 9 hours, the frog will be at 27 centimeters.

Since it takes 0.5 hours to climb 2 centimeters, it will take 0.25 hours to climb the final centimeter, and thus the frog will be on the top of the 28-centimeter pole in 9 + 0.25 = 9.25 hours.

Answer: C

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