My Math Forum  

Go Back   My Math Forum > High School Math Forum > Geometry

Geometry Geometry Math Forum


Reply
 
LinkBack Thread Tools Display Modes
January 18th, 2012, 06:33 AM   #11
Newbie
 
Joined: Jan 2012

Posts: 9
Thanks: 0

Re: Help with some pretty hard geometry issues

Yes, I finally got it! I'll post what I did!
So the first steps I followed were already mentioned by Denis.
Thus we get our second equation (first being 72=a+b+c) - c=7(b-a)

Now I continued, to find an equation that would define b for me!
a+b+7(b-a)=72
simplified: 4b-3a=36
b-3a/4=9
b=9+3a/4
b=(36+3a)/4

From this point, I used some logic, and realised that a,b and c are all integers, thus we must find such an a that if divided by 4, would be an integer. Which would be of course any multiple of 4.

Then I have made the following table (I subsituted the multiples of 4 into the following equations):
The equation would make sense only if a+b>c, c>a, c>b, a<b, and of course a/4?N, I ticked the equations that met those conditions, and written in red the condition they didn't meet.
72= a b c
72= 4 12 56 [color=#BF0000] a+b<c[/color]
72= 8 15 49 [color=#BF0000] a+b<c[/color]
72= 12 18 42 [color=#BF0000] a+b<c [/color]
72= 16 21 35 [color=#00BF00] ?[/color]
72= 20 24 28 [color=#00BF00] ?[/color]
72= 24 27 21 [color=#BF0000] a>c b>c[/color]
..... all higher as would be a higher number than c, so no point to continue.
Thus we get both solutions for this problem!

Thank you all for helping me out with the first steps!
matyasnovotny is offline  
 
Reply

  My Math Forum > High School Math Forum > Geometry

Tags
geometry, hard, issues, pretty



Search tags for this page
Click on a term to search for related topics.
Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Geometry hard roberthun Geometry 1 March 10th, 2013 08:18 AM
pretty hard inequality yo79 Math Events 1 January 15th, 2013 01:10 AM
Geometry Issues! Brightstar Geometry 3 January 19th, 2012 12:39 PM
Geometry problem help. (Pretty sure I've got it right.) sheepshead Geometry 1 February 12th, 2010 05:31 AM
Geometry, pretty difficult. Can you help/teach? Patricknolan Geometry 6 December 20th, 2009 01:22 AM





Copyright © 2019 My Math Forum. All rights reserved.