Maths Investigations

Posted Saturday, May 09, 2009 11:07 AM by kent-teachers

The Fido Think of a Number Puzzle from 7-up will grab your students attention.

http://www.digicc.com/fido/ 
(click the little guy in the bottom right to proceed to next page)

Do you or your students know how it works?  If anyone would like to tell us please leave a comment below.

Mandy :)

http://www.kented.org.uk/ngfl/

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Comments

# re: Maths Investigations

Saturday, May 20, 2006 11:53 AM by Pam Marsh

Ok, I'll rise. How does it work?

# re: Maths Investigations

Monday, May 22, 2006 12:43 PM by Mandy

Send me an email and I will tell you. I can't tell you on here as it will spoil it for others.
http://www.kented.org.uk/ngfl/contact/index.htm

# re: Maths Investigations

Thursday, May 25, 2006 11:47 AM by kent-teachers

Thanks for all your emails
Here is the solution for anyone else who would like to know:

When you subtract the two numbers, the sum of the digits of the answer is always a multiple of nine. (9,18,27,36,45,63,...)

Example 1: 742 - 247 = 495 (4+9+5=18)


You choose the 9.
495

Add the digits you did not choose (4+5=9) and subtract that sum from the first multiple of 9 above it (18) and the chosen digit will be revealed!

18 -  9 = 9

If you want to know more about the mathematics behind this visit:
http://mathforum.org/library/drmath/view/62561.html

# re: Maths Investigations

Monday, September 25, 2006 9:11 PM by Maths Investigation

Found this chap amazing- am going to try it with my year 2s tomorrow - know they will be gobsmaked!!

# re: Maths Investigations

Tuesday, November 14, 2006 2:42 PM by Bill

Thankyou. At first I really did think the Sprite boy could see what I was writing. I will use this on my next teaching practice.

# re: Maths Investigations

Thursday, July 26, 2007 9:21 PM by Ron Lisett

I am helping out in a maths summer school (4 half days) first time for me. I was searching for investigational work. Fido's puzzle is exactly the type of material I need. Thank you!

# re: Maths Investigations

Monday, March 10, 2008 5:18 PM by Nic

I have tried this twice and both times he got it wrong!! I triple checked my working out and it didin't work.  Is there any reason why?