test36 #11

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dunkin77: Master | Next Rank: 500 Posts; Posts: 269; Joined: Sun Apr 01, 2007 5:41 am

test36 #11

by dunkin77 » Sun Apr 29, 2007 1:53 pm

11. A point on the edge of a fan blade that is rotating in a plane is 10 centimeters from the center of the fan. What is the distance traveled, in centimeters, by this point in 15 seconds when the fan runs at the rate of 300 revolutions per minute ?
(A) 750π
(B) 1,500π
(C) 1,875π
(D) 3,000π
(E) 7,500π

The answer is B) - but for some reason my answer was A). Can you help?

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Source: Beat The GMAT — Problem Solving | Sun Apr 29, 2007 1:53 pm

jayhawk2001: Community Manager; Posts: 789; Joined: Sun Jan 28, 2007 3:51 pm; Location: Silicon valley, California; Thanked: 30 times; Followed by:1 members

Re: test36 #11

by jayhawk2001 » Sun Apr 29, 2007 6:20 pm

dunkin77 wrote:11. A point on the edge of a fan blade that is rotating in a plane is 10 centimeters from the center of the fan. What is the distance traveled, in centimeters, by this point in 15 seconds when the fan runs at the rate of 300 revolutions per minute ?
(A) 750π
(B) 1,500π
(C) 1,875π
(D) 3,000π
(E) 7,500π

The answer is B) - but for some reason my answer was A). Can you help?

In 60 seconds the fan rotates 300 times, so in 15 sec it will rotate
75 times.

Total distance covered = (perimeter of circle with radius as 10) * 75

= 2*pi*10 * 75
= 1500 * pi

Hence B

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Cybermusings: Legendary Member; Posts: 559; Joined: Tue Mar 27, 2007 1:29 am; Thanked: 5 times; Followed by:2 members

by Cybermusings » Mon Apr 30, 2007 12:48 am

A point on the edge of a fan blade that is rotating in a plane is 10 centimeters from the center of the fan. What is the distance traveled, in centimeters, by this point in 15 seconds when the fan runs at the rate of 300 revolutions per minute ?
(A) 750π
(B) 1,500π
(C) 1,875π
(D) 3,000π
(E) 7,500π

300 revolutions / min = 300 * 15/60 = 75 revolutions in 15 seconds
Distance of the point from center = 10 cm (or radius = 10)
1 revolution = 2*pie*r = 20*pie
Thus 75 revolutions = 75*20*pie = 1500pie

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8086; Joined: Sat Apr 25, 2015 10:56 am; Location: Los Angeles, CA; Thanked: 43 times; Followed by:29 members

by Scott@TargetTestPrep » Mon May 20, 2019 6:16 pm

dunkin77 wrote:11. A point on the edge of a fan blade that is rotating in a plane is 10 centimeters from the center of the fan. What is the distance traveled, in centimeters, by this point in 15 seconds when the fan runs at the rate of 300 revolutions per minute ?
(A) 750Ï€
(B) 1,500Ï€
(C) 1,875Ï€
(D) 3,000Ï€
(E) 7,500Ï€

The distance traveled by the point in one revolution is equal to the circumference of the circle, which is 2 x Ï€ x 10 = 20Ï€.

We must convert 300 revolutions per minute to revolutions per second: 300/60 = 5 revolutions per second. So in 15 seconds, the number of revolutions is 5 x 15 = 75 revolutions.

Thus, the total distance traveled is 20Ï€ x 75 = 1500Ï€.

Answer: B

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