Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

What is the radius of the inscribed circle to a triangle [#permalink]

Show Tags

27 Jan 2004, 13:19

00:00

A

B

C

D

E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct
0% (00:00) wrong based on 0 sessions

HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

What is the radius of the inscribed circle to a triangle whose sides measure
21cm, 72cm and 75cm respectively?
(1) 9 cm
(2) 37.5 cm
(3) 28.5 cm
(4) 14.5 cm
_________________

There is a formula for this but I dont remember. as we know the area of the triangle is 1/2 base * height and so the area is 1/2*21*76 = 756 and the area of the circle is phi r^2 which should be less than 756. So of the choices 37.5 and 28.5 is ruled out. Now left with 9 and 14. These can be the answers, in exam I would opt for 9 as the area is less and also is a multiple of 3 like the sides 21,72 and 75.

Since this is a right triangle the area is 21x72/2=756. The area of a triangle that has a circle inscribed is S=pr ( p-half the perimeter of triangle, r-radius of inscribed circle).P=168,(21+75+72) ,p=P/2=84 Then 756/84= r =9

Guys,
there is quick way to approximate right choice in this particular case.

You see, the diameter of incribed circle CANNOT be more than the least of the sides of a triangle. So the most value of the radius might be is 21/2=10.5 sm. Therefore, I pick (1) w/o any calculations.

General advice. See choices before rush into calculus.

Thank you. I agree with you on this given the choices. I was looking for radius < 21 and that was my error. But, what if both 9 and 10 were given in the choices?

I'd rather know of a property that helps me in the long run.