[ Divisibility by 11 ]

Kolya Vasin wrote down an example of multiplication, and then replaced all the digits with letters: the same digits with the same letters, and different digits with different letters. The resulting equation is $\overline{a b} \cdot \overline{c d}=\overline{e f f e}$. Did Kolya make a mistake?

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Apply the divisibility rule for 11.

## Solution

The factors are not divisible by 11, but the product is.

## Answer

I made a mistake.