Properties of Triangles 1 Question 7

7. If the angles of a triangle are in the ratio 4:1:1, then the ratio of the longest side to the perimeter is

(2003,1M)

(a) 3:(2+3)

(b) 1:3:2

(c) 1:2+3

(d) 2:3

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Answer:

Correct Answer: 7. (b)

Solution:

  1. Given, ratio of angles are 4:1:1.

4x+x+x=180

x=30A=120,B=C=30

Thus, ratio of longest side to perimeter =aa+b+c

 Let b=c=xa2=b2+c22bccosA [by cosine rule] a2=2x22x2cosA=2x2(1cosA)a2=4x2sin2A/2a=2xsinA/2a=2xsin60=3x

Thus, required ratio

=aa+b+c=3xx+x+3x=32+3=3:2+3



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