11) Calculate dist

Expert replies

ern5231: Master | Next Rank: 500 Posts; Posts: 226; Joined: Sun Aug 09, 2009 4:34 am

by ern5231 » Sat May 15, 2010 10:15 pm

A Semicircle is divided into 8 portions and has the points O to W. The semi circle has the length of 1 mile and a man starts at O travelling at 15 mph. In between what points will the man be after 3 minutes?

A. Q to R B. R to S C. S to T D. T to U E. U to V

Like this post

Source: Beat The GMAT — Problem Solving | Sat May 15, 2010 10:15 pm

akdayal: Senior | Next Rank: 100 Posts; Posts: 52; Joined: Thu Feb 25, 2010 9:08 am; Thanked: 5 times

by akdayal » Sat May 15, 2010 10:25 pm

it should be E

Like this post

dkumar.83: Senior | Next Rank: 100 Posts; Posts: 90; Joined: Thu Jan 14, 2010 5:42 am; Thanked: 2 times

by dkumar.83 » Sat May 15, 2010 10:37 pm

The circumference of the semicircle is (pi*r), which equals (pi*1/2) miles. Assuming pi=3. the distance comes to a little over 1.5 miles.
In 3 min the person would be covering a little over 3/4th of a mile (0.75 mile). This distance will be a little less than half of the distance calculated. hence the answer should be "B"; R to S.

Like this post

Gmat_War: Senior | Next Rank: 100 Posts; Posts: 41; Joined: Sun Apr 25, 2010 12:19 pm; Thanked: 2 times

by Gmat_War » Sat May 15, 2010 10:45 pm

the semicircle has a length of 1 mile and it is divided into 8 equal parts.So each part will equal to 1/8=0.125 mile
The speed of the man is 15mph.
Thus in 60 minutes it goes 15 miles.
Hence in 3 minutes it will go (15/60)*3=0.75 miles
If OP=0.125,OQ=0.250,OR=0.375,OS=0.5,OT=0.625,OU=0.750
So at 3 minutes,he will be at point U
=>After 3 minutes he will be between U and V,that is option E

Like this post

dkumar.83: Senior | Next Rank: 100 Posts; Posts: 90; Joined: Thu Jan 14, 2010 5:42 am; Thanked: 2 times

by dkumar.83 » Sat May 15, 2010 11:07 pm

one question: what does the length of semicircle mean?

1. is it pi*r ?
2. or is it (pi*r+diameter) ?

Like this post

indiantiger: Master | Next Rank: 500 Posts; Posts: 362; Joined: Fri Oct 02, 2009 4:18 amFollowed by: 1 member; Thanked: 26 times

by indiantiger » Sun May 16, 2010 4:48 am

I have assumed that length means circumference of the semicircle = 1 mile
8 equal partitions are
o-p,p-q,q-r,r-s,s-t ,t-u,u-v,v-w
Now each is equal to 1/8 of a mile.

to cover one of the partitions it will take 1/8/(15) = 60/8*15 = 4/8 = 1/2 minute
time taken to cover o-p = 1/2
p-q =1/2 (total time =1)
q-r = 1/2 (total time =1.5)
r-s= 1/2 (total time = 2.0)
s-t = 1/2(total time = 2.5)
t-u = 1/2(total time = 3.0)
u-v (person will be here at the starting point that is u) (E)
v-w

Like this post

Stuart@KaplanGMAT: GMAT Instructor; Posts: 3225; Joined: Tue Jan 08, 2008 2:40 pmFollowed by: 614 members; Location: Toronto; Thanked: 1710 times; GMAT Score:800

by Stuart@KaplanGMAT » Sun May 16, 2010 9:09 am

ern5231 wrote:A Semicircle is divided into 8 portions and has the points O to W. The semi circle has the length of 1 mile and a man starts at O travelling at 15 mph. In between what points will the man be after 3 minutes?

A. Q to R B. R to S C. S to T D. T to U E. U to V

Hi,

I'm not sure from where you got this problem, but you'll never see something this poorly worded in the GMAT.

First, what does "length" of the semi-circle mean? Circumference of the arc? Diameter? Radius? Circumference of the arc plus the diameter?

Second, nowhere does it say that the 8 portions are equal or where the points are located; are they all located on the arc? Are some of them located on the diameter?

Without clarification, there's no way to answer the question.

What's the source of the question?

Stuart Kovinsky | Kaplan GMAT Faculty | Toronto

Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course

Like this post

dkumar.83: Senior | Next Rank: 100 Posts; Posts: 90; Joined: Thu Jan 14, 2010 5:42 am; Thanked: 2 times

by dkumar.83 » Sun May 16, 2010 10:33 am

Hey stuart,

I totally agree, and that is the reason i am highly confused. I have got this from a friend of mine. Maybe its incorrect.

Thanks anyways.

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

559 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review