AustinKL wrote:

A ball drops from a certain height. The height it will reach after rebounding from the floor is 80 percent of the previous height. The total travel is 3,104cm when it touches the floor on the third time. What is the value of the original height, in cm?

A. 400cm

B. 500cm

C. 600cm

D. 700cm

E. 800cm

Let x be the ball's original heightSo, x = distance of the ball's first DROP

And 0.8x = distance of the ball's first RISE

0.8x = distance of the ball's second DROP

(0.8)(0.8x) = distance of the ball's second RISE

(0.8)(0.8x) = distance of the ball's third DROP

At this point, the ball touches the ground for the third time.

So, the TOTAL distance = x + 0.8x + 0.8x + (0.8)(0.8x) + (0.8)(0.8x) = 3104 cm

Simplify: x + 0.8x + 0.8x + 0.64x + 0.64x = 3104 cm

Simplify: 3.88x = 3104

Solve: x = 800

Answer: E

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Brent Hanneson – Founder of gmatprepnow.com