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**jacks****Member**- Registered: 2012-11-21
- Posts: 132

A 4 digit no. abcd is such that 4 *(abcd) = (dcba). Then no. abcd is

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**anonimnystefy****Real Member**- From: Harlan's World
- Registered: 2011-05-23
- Posts: 16,037

I have that abcd=2178.

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

Hi;

Yes, and that is the only solution.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

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**jacks****Member**- Registered: 2012-11-21
- Posts: 132

Yes 2178 is right answer.

How can i get it.

would you like to explain me

hanks

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**bobbym****bumpkin**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606

Hi;

First thing that jumps right out at you is that the front digit is either a 1 or 2. So, the last digit is a 4 or an 8. You now only have to try 16 numbers to find all the answers.

**In mathematics, you don't understand things. You just get used to them.****If it ain't broke, fix it until it is.**** Always satisfy the Prime Directive of getting the right answer above all else.**

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**phrontister****Real Member**- From: The Land of Tomorrow
- Registered: 2009-07-12
- Posts: 4,592

Hi,

**a** = 2...from **d** x 4 = even, and **a** x 4 must be a single-digit result (to avoid a 5-digit end product).**b** = 1...from **b** x 4 must be a single-digit result (to keep **a** = 2), and 2 is already taken.**d** = 8...from **a** x 4 = 8.**c** = 7...from (**c** x 4) + the tens unit (3) from **d** x 4 must end in 1, which is only possible with **c** = 7 or 2; but 2 is already taken.

So, abcd is 2178.

"The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do." - Ted Nelson

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**jacks****Member**- Registered: 2012-11-21
- Posts: 132

Thanks friends got it

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