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**jacks****Member**- Registered: 2012-11-21
- Posts: 126

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: 16,016

I have that abcd=2178.

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 105,308

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.****No great discovery was ever made without a bold guess. **

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**jacks****Member**- Registered: 2012-11-21
- Posts: 126

Yes 2178 is right answer.

How can i get it.

would you like to explain me

hanks

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 105,308

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.****No great discovery was ever made without a bold guess. **

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**phrontister****Real Member**- From: The Land of Tomorrow
- Registered: 2009-07-12
- Posts: 4,400

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.

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**jacks****Member**- Registered: 2012-11-21
- Posts: 126

Thanks friends got it

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