### Brain Teasers

# Five Pound Seventy Pence

Mad Ade was in his local news agents looking at the various magazines on display, He picked a copy of "Kebabs and Me" a copy of "Everything You Ever Wanted to Know About Nylon Underpants" and a copy of "Indoor Hang Gliding". He passed the magazines to the shop keeper, who duly entered the amounts of each magazine into the till. "Wow, hang on a minute" said Mad Ade. "You just pressed the multiplication button each time between amounts instead of the addition button." The shop keeper smiled with new false teeth and replied, "it doesn't matter either way, it still comes to £5.70p".

What were the prices of the magazines, that could either be multiplied or added to make £5.70

What were the prices of the magazines, that could either be multiplied or added to make £5.70

### Answer

£2.85*£1.60*£1.25= £5.70£2.85+£1.60+£1.25=£5.70

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## Comments

Jul 02, 2002

I made it 1.90 each it does not say different ammounts for each magazine

1.90 doesn't work

1.90*1.90*1.90=6.859

"Everything you ever wanted to know about nylon underpants"... hahahahahaha. Nice teaser too ;).

I c that the answer works, but how do you find it?

by clicking the show answer button

Dec 28, 2006

I see the answer but can you post the algebra used to solve it. This problem is driving me insain!

When Mad-Ade says 'by clicking the answer button' he means on the site where he stole the teaser from becasue he doesn't know how to solve this problem.

Here is how I did it (you can fill in the detail).

Firstly, since they all can't be $1.90 then at least one must be more and at least one must be less.

So I made a spreadsheet starting from $1.90 and stepping down in 5 pence decrements. It is highly unlikely that the amounts will be in single digit pennies less than $.05 because it will be difficult to get the product to end in 0.70 given that 6 decimal places will be generated.

Now having selected one possibilty, subtracting from 5.7 leaves the sum of the other 2 and dividing 5.7 by the estimate gives the product of the other 2.

Quadratic equation theory tells us that any 2 numbers can be found given their sum and product using the quadratic formula.

7 steps of the spreadsheet gave me the answer.

pm me if you would like more details.

Here is how I did it (you can fill in the detail).

Firstly, since they all can't be $1.90 then at least one must be more and at least one must be less.

So I made a spreadsheet starting from $1.90 and stepping down in 5 pence decrements. It is highly unlikely that the amounts will be in single digit pennies less than $.05 because it will be difficult to get the product to end in 0.70 given that 6 decimal places will be generated.

Now having selected one possibilty, subtracting from 5.7 leaves the sum of the other 2 and dividing 5.7 by the estimate gives the product of the other 2.

Quadratic equation theory tells us that any 2 numbers can be found given their sum and product using the quadratic formula.

7 steps of the spreadsheet gave me the answer.

pm me if you would like more details.

huh? ok no..i don't have the brains for this...

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