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 Posted: Thu May 09, 2013 12:02 pm

Joined: Thu Oct 18, 2012 9:41 am
Posts: 444
A farmer has three goats, A, B, and C. Each goat is a different weight and is an exact number of kilograms. Goats A and B weigh a total of 20kg. Goats B and C weigh a total of 15kg. Goats A and C weigh a total of 17 kg.

What is the weight of each goat?

Is there a simple way to do this?

Sleepy

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 Posted: Thu May 09, 2013 12:14 pm

Joined: Sat Apr 17, 2010 2:53 pm
Posts: 138
Because of the last two statements, Goat A weighs 2kg more than B.

So what two numbers make 20 that are '2 apart'? Answer 9 & 11.

Therefore A is 11kgs and B 9kgs. It then follows easily C weighs 6kg.

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 Posted: Thu May 09, 2013 12:16 pm

Joined: Thu Oct 18, 2012 9:41 am
Posts: 444
thank you secondtime, you make it look so easy.

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 Posted: Thu May 09, 2013 12:49 pm

Joined: Mon Aug 22, 2011 8:20 pm
Posts: 1706
Location: Warwickshire
Another simple way is to add 20kg + 15kg + 17kg = 52kg.
That will be double the total weight of all three goats as it is (A+B) + (B+C) + (A+C) - or 2 (A+B+C)
So the total of all 3 will be 26kg

We know A+B = 20kg - so C must be 6kg (i.e. 26kg-20kg)
We know B+C = 15kg - so A must be 11kg (i.e. 26kg-15kg)
We know A+C = 17kg - so B must be 9kg (i.e. 26kg-17kg)

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 Posted: Thu May 09, 2013 2:20 pm

Joined: Tue Jul 21, 2009 9:56 pm
Posts: 8545
Great question. Which book is this from? Does it contain others which are as good as this?

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 Posted: Thu May 09, 2013 4:49 pm

Joined: Thu Oct 18, 2012 9:41 am
Posts: 444
Hi Mystery

I have Pmed you the link to the book

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 Posted: Thu May 09, 2013 5:01 pm

Joined: Thu Oct 18, 2012 9:41 am
Posts: 444
Thank you Okanagan, that's a great method . Will explain both to DD

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 Posted: Thu May 09, 2013 5:07 pm

Joined: Thu Oct 18, 2012 9:41 am
Posts: 444
Mystery,

There's another question in the same book (later on) so DD hasn't done this yet.. but here it is anyway

"Rosie bought three different hats. The red hat and the green hat cost a total of £16. The white hat and the green hat cost a total of £13. The white had and the red hat cost a total of £15. What is the cost of each hat?"

This appears on a level 4 paper too.

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 Posted: Fri May 10, 2013 11:22 am

Joined: Sun Oct 21, 2012 5:10 pm
Posts: 34
Hi Mystery

I have Pmed you the link to the book

I have Pmed you.
thanks

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 Posted: Fri May 10, 2013 8:34 pm

Joined: Tue Nov 27, 2012 1:26 pm
Posts: 1
Kindly PM me the link of the book.

Regards

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