BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

math question

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 117
Joined: Mon Oct 27, 2008 5:08 pm
Thanked: 1 times

math question

by [email protected] » Tue Oct 28, 2008 5:46 pm
A thin piece of wire 40 meters long is cut into tow pieces. one piece is used to form a circle with radius r, and the other is used to form a square. No wire is left over. Which of the following represents the total area, in meters, of the circular and the square regions in the term of r?
1 pi*r^2
2. pi*r^2 +10
3. pi*r^2 +1/4pi^2*r^2
4. pi*r^2+(40-2pi r)^2
5. pi*r^2+(10-1/2pi*r)2
Top
Source: — Problem Solving |
User avatar
Legendary Member
Posts: 519
Joined: Sat Jan 27, 2007 7:56 am
Location: India
Thanked: 31 times

by Neo2000 » Tue Oct 28, 2008 6:08 pm
Area of circle of radius r = pi*r^2

Amount of wire used up in making circle = 2*ppi*r

Amount of wire left = 40 - 2*pi*r
This is also the perimeter of the Square

Therefore side of Square = (40 - 2*pi*r)/4 = 10- (1/2)pi*r
Area = (10- (1/2)pi*r) ^2

Total area = pi*r^2 + (10- (1/2)pi*r)^2
Top
Post new topic Post Reply
• Page 1 of 1