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 Post subject: Maths question
PostPosted: Fri Dec 12, 2008 6:43 pm 
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Joined: Sat Dec 06, 2008 1:41 pm
Posts: 136
Please can someone help with this problem question

The money in Tim's wallet consists entirely of 2p and 5p coins. Sam asked him if he could change a £1 coin, but he was not able to do it exactly. What is the greatest amount of money that Tim could have in his wallet?

DD insists it is £1.04. Answer in booklet is £1.03.

DD's explanation:

99p is where she stopped using 2p and 5 p coins. But since the question asked for greatest amount, DD added another 5p coin to make £1.04.

DD said that this way, even though Tim has £1.04, he still cannot give Sam change of £1 exactly, but can only manage 99p, with the extra 5p coin hindering his (Tim's) objective of wanting to give Sam the exact change.

I am completely lost myself, as I had thought the answer was 99p.


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 Post subject:
PostPosted: Fri Dec 12, 2008 7:08 pm 
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Joined: Mon Feb 12, 2007 1:21 pm
Posts: 11931
if you had £1.04 you would have 2x2p somewhere so you could give change for £1.

99p = 19x 5p (say) + 4p

add another 5p and you can give the 20 5p coins.


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 Post subject:
PostPosted: Fri Dec 12, 2008 7:34 pm 
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Joined: Fri Jul 06, 2007 8:31 pm
Posts: 1192
Clearly 20 x 5p gives £1

But 19 x 5 gives a nice odd number... 95p

Bearing in mind 18 x 5 = 90p and we have 19 5ps so having 5x 2p would also bring us to £1; we must therefore have less than 5 2ps otherwise we would have reached £1 via the 18 x 5p route.

Therefore 19 x 5 + 4 x 2 is the max

i.e. £1.03

Tricky question

Regards
SVE

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Animis opibusque parati


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PostPosted: Fri Dec 12, 2008 8:17 pm 
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Joined: Sat Dec 06, 2008 1:41 pm
Posts: 136
Ok. We get it now. Thanks guys!


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 Post subject:
PostPosted: Fri Dec 12, 2008 8:18 pm 
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Joined: Sun Oct 05, 2008 6:37 pm
Posts: 50
Or..

49*2 + 1*5 = 1.03
3*2 + 19*5=1.01

I suspect it is highest remainder for 100 by either 2 or 5 + 5 or 2

i.e 95+ 3*2 or 98+1*5

as they wanted highest it has to be 1.03
epp


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