• 7 CATs FREE!
    If you earn 100 Forum Points

    Engage in the Beat The GMAT forums to earn
    100 points for $49 worth of Veritas practice GMATs FREE

    Veritas Prep
    VERITAS PRACTICE GMAT EXAMS
    Earn 10 Points Per Post
    Earn 10 Points Per Thanks
    Earn 10 Points Per Upvote
    REDEEM NOW
This topic has expert replies
Newbie | Next Rank: 10 Posts
Posts: 3
Joined: 02 Dec 2010

Tunnel

by kalpak.ranadive » Wed Dec 08, 2010 9:23 am
Hi... Can anyone help me out with the below question?

Thanks....

Image

User avatar
Community Manager
Posts: 991
Joined: 23 Sep 2010
Location: Bangalore, India
Thanked: 146 times
Followed by:24 members

by shovan85 » Wed Dec 08, 2010 9:42 am
If it were a complete circle then the missing part of the circle is 1/4 of the circle.

Full circle subtends 360 deg in center.
1/4 of the circle subtends 90 deg in center.

Now draw a triangle with the straight line shown 12 ft as base. Then it will be a isosceles triangle with 90 at origin. It becomes isosceles because the other two sides are radius.

Thus r^2 + r^2 = 12^2

=> 2r^2 = 144

=> r^2 = 72

=> r = 6(2)^1/2

Thus the perimeter of circle = 2 * pie * 6(2)^1/2

Then 3/4th of the circle perimeter = 3/4 * [2 * pie * 6(2)^1/2]

Thus answer = 9 * pie * (2)^1/2

IMO C
If the problem is Easy Respect it, if the problem is tough Attack it

Newbie | Next Rank: 10 Posts
Posts: 3
Joined: 02 Dec 2010

by kalpak.ranadive » Wed Dec 08, 2010 9:47 am
shovan85 wrote:If it were a complete circle then the missing part of the circle is 1/4 of the circle.

Full circle subtends 360 deg in center.
1/4 of the circle subtends 90 deg in center.

Now draw a triangle with the straight line shown 12 ft as base. Then it will be a isosceles triangle with 90 at origin. It becomes isosceles because the other two sides are radius.

Thus r^2 + r^2 = 12^2

=> 2r^2 = 144

=> r^2 = 72

=> r = 6(2)^1/2

Thus the perimeter of circle = 2 * pie * 6(2)^1/2

Then 3/4th of the circle perimeter = 3/4 * [2 * pie * 6(2)^1/2]

Thus answer = 9 * pie * (2)^1/2

IMO C

THANKS :)