Horse question

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vinviper1: Master | Next Rank: 500 Posts; Posts: 222; Joined: Tue Mar 25, 2008 3:52 pm; Thanked: 2 times

Horse question

by vinviper1 » Tue Jul 22, 2008 10:05 am

Four horses are tethered at 4 corners of a square field of side 70 ft so that they just cannot reach one another. The area left ungrazed by the horses is:

A. 1050 sq.ft
B. 3850 sq. ft
C. 950 sq. ft
D. 1075 sq.ft
E. 1200 sq. ft

Ans is A

Quote

Source: Beat The GMAT — Problem Solving | Tue Jul 22, 2008 10:05 am

sudhir3127: Legendary Member; Posts: 829; Joined: Mon Jul 07, 2008 10:09 pm; Location: INDIA; Thanked: 84 times; Followed by:3 members

by sudhir3127 » Tue Jul 22, 2008 10:30 am

we need to find the length of the rope in which the horses tied

it should be equal to half of the side of the square plot so that they just cannot reach one another.

Therefore
the length of the rope is 35m (70/2).

The area covered by each horse should be equal to the area of circle with radius of 70/2 = 35m(length of the rope).

Area left ungrazed by the horses = Area of square field - Area covered by four horses.

= 70^2 - (22/7)*35*35 = 4900 - 3850 = 1050 sq.m.