R,T,U...circle

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puneetdua: Senior | Next Rank: 100 Posts; Posts: 87; Joined: Wed Jun 16, 2010 7:57 pm; Location: Delhi,India; Thanked: 1 times

by puneetdua » Sat Sep 18, 2010 6:46 am

Hi

This Question is already discussed - but want to discuss one more time so opening a new thread -

The points R, T, and U lie on a circle that has radius 4. If the length of arc RTU is 4*Pi/3 , what is the length of line segment RU?

A. 4/3
B. 8/3
C. 3
D. 4
E. 6

i was solving the below mentioned way -

Radius - 4
So circumfrence - 2*Pi*R -> 8*Pi

Length of RTU - > 4*Pi/3

So length of RU shd be circumfrence - RTU -> 8*Pi -4*Pi/3

but this is not working, not able to get answer as mentioned in choices.

Can you please elaborate - how am doing it wrong and can you please suggest solution also .

Thanks
Puneet

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Source: Beat The GMAT — Problem Solving | Sat Sep 18, 2010 6:46 am

diebeatsthegmat: Legendary Member; Posts: 1119; Joined: Fri May 07, 2010 8:50 amFollowed by: 3 members; Thanked: 29 times

by diebeatsthegmat » Sat Sep 18, 2010 9:42 am

puneetdua wrote:Hi

This Question is already discussed - but want to discuss one more time so opening a new thread -

The points R, T, and U lie on a circle that has radius 4. If the length of arc RTU is 4*Pi/3 , what is the length of line segment RU?

A. 4/3
B. 8/3
C. 3
D. 4
E. 6

i was solving the below mentioned way -

Radius - 4
So circumfrence - 2*Pi*R -> 8*Pi

Length of RTU - > 4*Pi/3

So length of RU shd be circumfrence - RTU -> 8*Pi -4*Pi/3

but this is not working, not able to get answer as mentioned in choices.

Can you please elaborate - how am doing it wrong and can you please suggest solution also .

sorry, i will do my way then you see where your solution is wrong, ok? consider O is the center of the circle
length of arc RTU=angle O/360*2*r=4p/3
so angle O=4p*360/3*8p=60
thus triangle ROU=tiangle ROT and triangle TOU
so RO=UO=RU=4

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puneetdua: Senior | Next Rank: 100 Posts; Posts: 87; Joined: Wed Jun 16, 2010 7:57 pm; Location: Delhi,India; Thanked: 1 times

by puneetdua » Sat Sep 18, 2010 9:53 am

ahhhh... Thanks ..i got the question now ....

its what is the length of line segment RU?

i was taking it as what is the length of ARC RU..!!!!

need to read statement with more concentration.

anyways - Thanks diebeatsthegmat, your post has shown me my mistake.

Thanks
Puneet

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