Go to navigation
It is currently Wed Dec 07, 2016 6:20 pm

All times are UTC




Post new topic Reply to topic  [ 6 posts ] 
Author Message
PostPosted: Sun Aug 12, 2012 2:15 pm 
Offline

Joined: Wed Mar 09, 2011 2:22 pm
Posts: 710
I don't understand the given answer to the final question on this paper!! Does anyone remember this one from having looked at past papers? I'll write it out here...

The diagram shows a circle with circumference of 1cm being rolled around an equilateral triangle with sides of length 1cm.

How may complete turns does the circle make as it rolls around the triangle (without slipping) to its original starting position?


What do you think??


Top
 Profile  
 
PostPosted: Sun Aug 12, 2012 2:22 pm 
Offline

Joined: Fri Sep 15, 2006 8:51 am
Posts: 8113
Manana wrote:
I don't understand the given answer to the final question on this paper!! Does anyone remember this one from having looked at past papers? I'll write it out here...

The diagram shows a circle with circumference of 1cm being rolled around an equilateral triangle with sides of length 1cm.

How may complete turns does the circle make as it rolls around the triangle (without slipping) to its original starting position?


What do you think??


I would have thought 3.. is that the answer?

the circumference of the circle is one cm and hence if rolled round the edges would go 1cm to get it back a complete circle. The total length of the sides of the triangle is 3cms so 3 revolutions?


Top
 Profile  
 
PostPosted: Sun Aug 12, 2012 3:09 pm 
Offline

Joined: Wed Mar 09, 2011 2:22 pm
Posts: 710
hermanmunster wrote:
Manana wrote:
I don't understand the given answer to the final question on this paper!! Does anyone remember this one from having looked at past papers? I'll write it out here...

The diagram shows a circle with circumference of 1cm being rolled around an equilateral triangle with sides of length 1cm.

How may complete turns does the circle make as it rolls around the triangle (without slipping) to its original starting position?


What do you think??


I would have thought 3.. is that the answer?

the circumference of the circle is one cm and hence if rolled round the edges would go 1cm to get it back a complete circle. The total length of the sides of the triangle is 3cms so 3 revolutions?


Yes-DS, DH and I all thought 3, but the answer sheet says 4?! It's a 2 mark question as well?!!


Top
 Profile  
 
PostPosted: Sun Aug 12, 2012 3:15 pm 
Offline

Joined: Fri Sep 15, 2006 8:51 am
Posts: 8113
hmmm - sounds like time for some gooogling:



http://wiki.answers.com/Q/The_circle_ha ... ting_posit

4!! we weren't allowing for having to do a 360 degree turn at the corners ! Duh! :mrgreen:


Top
 Profile  
 
PostPosted: Sun Aug 12, 2012 4:29 pm 
Offline

Joined: Mon Feb 12, 2007 1:21 pm
Posts: 11948
Every shape will have an extra 'turn' because the external angles of a shape are 360 degrees.


Top
 Profile  
 
PostPosted: Mon Aug 13, 2012 9:33 am 
Offline

Joined: Wed Mar 09, 2011 2:22 pm
Posts: 710
hermanmunster wrote:
hmmm - sounds like time for some gooogling:



http://wiki.answers.com/Q/The_circle_ha ... ting_posit

4!! we weren't allowing for having to do a 360 degree turn at the corners ! Duh! :mrgreen:


Doh-yes, of course! That makes perfect sense to me as a 35 year old (who has seen the answer and had it explained to me!); I will see what DS says!!

I sort of imagined it pivoting at the corners but obviously didn't think deeply enough about it!


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 6 posts ] 

All times are UTC


Who is online

Users browsing this forum: jumpingjack and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
CALL 020 8204 5060
   
Privacy Policy | Refund Policy | Disclaimer | Copyright © 2004 – 2016