Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have a question regarding triangles which is puzzling me:

In triangle PQR , PR=7 and PQ=4.5 . Which of the following cannot represent the length of QR ? a)2.0 , b)3 , c)3.5 , d)4.5 , e)5.0

Any suggestions ?

share|cite|improve this question
What do you know about the sum of the sides of a triangle with respect to the remaining side? – Pedro Tamaroff Jun 18 '12 at 21:16
up vote 2 down vote accepted

The sum of the two smaller sides must be greater than the last side.
So 2 can't be the length of QR : 2+4.5=6.5<7

share|cite|improve this answer
Not surprisingly, this restriction is called the triangle inequality. – lhf Jun 18 '12 at 21:17
Thanks for pointing that out.. I'll definitely keep this in mind – MistyD Jun 18 '12 at 21:18

Any set of three lengths can represent the sides of a triangle provided the largest is smaller than the other two combined.

Therefore, the answer is (a) 2.0. The length PR of 7 is too long to support sides of 4.5 and 2.0.

share|cite|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.