Jump to content
BrainDen.com - Brain Teasers
  • 0


Guest
 Share

Question

Here is a problem that I'd like someone to show me the path. Given: The difference between the squares of 2 consecutive multiples of three is 1989. Show the work for the solution.

First I made a list of the multiples of 3:................... 3, 6, 9, 12, etc...I noticed that there is a difference of 3.

Then I made a list of the squares of the multiples of 3:.. 9, 36, 81, 144, etc...I noticed that every term is divisible by 9

Then I tried to find the subtractive pairs that would give me the difference of 1989. Then I ran into the wall.

Edited by NuttyNumbers
Link to comment
Share on other sites

2 answers to this question

Recommended Posts

  • 0
You don't need to make those lists. Lets call the first number "x". That makes the othe number "x+3". (x+3)^2-x^2=1989. This becomes x^2+6x+9-x^2=1989. The "x^2"s cancel each other out leaving you with 6x+9=1989. I think you know how to finish this.

Hmmm, I see your reasoning now. So if the firs number is x, then the next number is x+3 since it is a multiple of 3. The other part is to square each term and set the terms in the equation form. Impressive, Thalia. You are a math GENIUS! Thanks.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Answer this question...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...