Gmat prep similar triangles

This topic has expert replies
Source: — Problem Solving |

Master | Next Rank: 500 Posts
Posts: 418
Joined: Wed Jun 11, 2008 5:29 am
Thanked: 65 times

by bluementor » Tue May 05, 2009 12:31 am
Lets say:

height of small triangle = h
height of big triangle = H

we know that:
base of small triangle = s
base of big triangle = S

Area of big triangle = 2 x Area of small triangle
(1/2)*H*S = 2*(1/2)*h*s

Since both triangles are similar (their internal angles are identical), the ratio of the corresponding lengths must be equal:

s/S = h/H

So,

(1/2)*H*S = 2*(1/2)*h*s
H*S = 2*h*s
S = 2*s*(h/H)
S = 2*s*(s/S)
S^2 = 2*(s^2)
S = (√2)*s

Choose C.

-BM-

Senior | Next Rank: 100 Posts
Posts: 59
Joined: Tue May 05, 2009 1:58 am
Thanked: 1 times

by Pranay » Tue May 05, 2009 2:17 am
bluementor wrote:Lets say:

height of small triangle = h
height of big triangle = H

we know that:
base of small triangle = s
base of big triangle = S

Area of big triangle = 2 x Area of small triangle
(1/2)*H*S = 2*(1/2)*h*s

Since both triangles are similar (their internal angles are identical), the ratio of the corresponding lengths must be equal:

s/S = h/H

So,

(1/2)*H*S = 2*(1/2)*h*s
H*S = 2*h*s
S = 2*s*(h/H)
S = 2*s*(s/S)
S^2 = 2*(s^2)
S = (√2)*s

Choose C.

-BM-