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How long would it take for ball moving in a straight line

This topic has 1 expert reply and 0 member replies

How long would it take for ball moving in a straight line

Post Fri Dec 08, 2017 7:03 am
How long would it take for ball moving in a straight line to travel 246 meters?

(1) It takes the ball 2 seconds to make 1 rotation.
(2)The ball makes 7 rotations per meter.

The OA is C.

Why do I need statement (2) to solve this DS question? I don't know how to use statement(1). Experts, can you give me your help? Thanks.

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GMAT/MBA Expert

Top Reply
Post Sat Dec 09, 2017 2:45 pm
Hi VJesus12,

We're asked how long it would take for a ball moving in a straight line to travel 246 meters.

1) It takes the ball 2 seconds to make 1 rotation.

Fact 1 gives us some information about the 'speed' of the ball, but we don't know how much distance is traveled by 1 rotation.
Fact 1 is INSUFFICIENT.

2)The ball makes 7 rotations per meter.

Fact 2 tells us how much distance is traveled by 1 rotation (re: 1/7 meter) but does not tell us anything about the 'speed' of the ball.
Fact 2 is INSUFFICIENT.

Combined, we know the speed of the ball in rotations and seconds (14 seconds to travel 1 meter), so we CAN determine how long it would take to travel 246 meters. While we don't have to actually do the math, the equation would be:
246 meters = (1/14 meter per second)(X seconds)
Combined, SUFFICIENT.

Final Answer: C

GMAT assassins aren't born, they're made,
Rich

_________________
Contact Rich at Rich.C@empowergmat.com

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