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# help

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

Find the four-digit number ABCD.

May 24, 2020

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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