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March 31st, 2008, 12:54 PM  #1 
Member Joined: Aug 2007 Posts: 39 Thanks: 0  Upper lower bounds
unladen, a lorry weighs 2.3 tonnes, measured to the nearest 100kg. the lorry is loaded with crates, each weighing 250kg, correct to the nearest 10kg. On its journey the lorry crosses a brdige with a maximum safe load of 15 tonnes. what is the maximum number of crates that the driver can load onto the lorry? its an upper and lower bounds question. the answer in the book says 49, but I dont quite understand how you get there. i thought you would use the lower bound on lorry and the lower bound of the crates so that you can have more crates, but the text book obviously diagrees. can somebody explain how to get to 49 and what it is that i'm doing wrong? 
March 31st, 2008, 01:46 PM  #2  
Global Moderator Joined: May 2007 Posts: 6,581 Thanks: 610  Re: Upper lower bounds Quote:
 
March 31st, 2008, 03:06 PM  #3  
Global Moderator Joined: Nov 2006 From: UTC 5 Posts: 16,046 Thanks: 938 Math Focus: Number theory, computational mathematics, combinatorics, FOM, symbolic logic, TCS, algorithms  Re: Upper lower bounds Quote:
However, when I work out the problem I get only 48 crates. I wonder where your book got 49?  
March 31st, 2008, 10:42 PM  #4 
Member Joined: Aug 2007 Posts: 39 Thanks: 0 
thanks for the help, i reckon the book is wrong 
April 1st, 2008, 09:42 AM  #5 
Global Moderator Joined: Dec 2006 Posts: 19,508 Thanks: 1741 
The book also seems to assume that the driver fully loads the lorry before driving it across the bridge, but there's nothing in the question to prevent him from fully loading it only after crossing the bridge.


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