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\(\begin{array} {lr} & ABCD \\ \times & 9 \\ \hline & DCBA \end{array}\)

 

Find the four-digit number ABCD.

 May 24, 2020
 #1
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A has to be 1 because anything larger would put five digits in the product. 

 

The 1 at the end of the product means that D is 9. 

 

B has to be 0 because anything else would carry over to the A and put five digits in the product. 

 

Since B is 0 and you carried 8 over from the D, C has to be 8. 

 

       1 0 8 9  

       x        9   

       ———–  

        9 8 0 1   

 

A  =  1 

B  =  0 

C  =  8 

D  =  9

 

I think that works 

.

 May 24, 2020

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