Go to navigation
It is currently Wed Dec 07, 2016 10:14 pm

All times are UTC




Post new topic Reply to topic  [ 3 posts ] 
Author Message
PostPosted: Sun Aug 28, 2011 1:40 pm 
Offline

Joined: Tue Jul 31, 2007 9:37 am
Posts: 408
Hi

DS1 and I are thrown with the following question. Can anyone shed light on the rationale, please:

Library A had 86 more books than library B. 12 books were moved from library A to library B. How many fewer books were there in library B than in library A now?

NB, the key is in the last line - how many fewer books in library B (As Is situation) than library A (To Be situation).

FYI, I think the answer is 62


Top
 Profile  
 
PostPosted: Sun Aug 28, 2011 4:04 pm 
Offline

Joined: Wed Aug 25, 2010 2:58 pm
Posts: 496
Yes, I agree with your maths!

So if Library A has 86 more books than Library B the easiest way of showing this is...
A=86
B=0

Then 12 books are taken from A and given to B
A=74
B=12

So the difference is 62!


Top
 Profile  
 
PostPosted: Thu Sep 01, 2011 8:59 pm 
Offline

Joined: Tue Jul 21, 2009 9:56 pm
Posts: 8228
It's quite a good question. Maths is right. If it's any help to the child you can think about it slightly differently, but get same answer. If you move 12 books from library A to library B you increase B by 12 and decrease A by 12 so you change the difference between the two libraries by 24.

You are reducing the difference as originally A had 86 more than B. So the new difference is 86-24 = 62. I guess many children will give 74 as the answer as when working quickly one might think that when you shift one book from A to B you change the difference by 1, whereas you change the difference by 2 as one goes up by one and one goes down by 1. Could do it with smaller numbers of biscuits on two plates if child is not convinced. Every time you move one biscuit from one plate to the other the difference between the two plates changes by 2.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 3 posts ] 

All times are UTC


Who is online

Users browsing this forum: No registered users and 3 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