Another math problem

Discus: SAT/ACT Tests and Test Preparation: July 2004 Archive: Another math problem
 By Legendofmax (Legendofmax) on Sunday, July 11, 2004 - 03:27 pm: Edit

http://img23.exs.cx/img23/7505/math.png

 By Frs (Frs) on Sunday, July 11, 2004 - 03:37 pm: Edit

sqrt(27) or 3sqrt(3), however you prefer.

In order to solve this, you have to know the formula for an altitude of an equilateral triangle is (sqrt(3)/2)s.

 By Feuler (Feuler) on Sunday, July 11, 2004 - 03:39 pm: Edit

Draw a line from D perindicular to BC and you're basically done. The answer is A.

You do not have to "know" anything as long as you have an intuitive grasp of geometry, which is why it is much more important to understand than to memorize, despite how we seem to like to teach math in this country.

 By Legendofmax (Legendofmax) on Sunday, July 11, 2004 - 03:46 pm: Edit

I got the correct answer but I did in an embarrassingly longer fashion... I always do such problems in a manner that makes it more difficult than it really is, hah. Keep forgetting about altitudes XD Tis the only problem I missed on this practice SAT I just took.

 By Eecs (Eecs) on Sunday, July 11, 2004 - 03:51 pm: Edit

actually, all you gotta do for that one is notice the whole triangle is a 30-60-90 triangle.

since ABD is equilateral, AD is also 3.
since D is the midpoint of AC, AD=DC, so DC=3.

that would make AB 3, AC 6, so BC has to be 3sqrt(3)