Hello, janvdl!

Apparently there has to be a rule for multiplying by 17,

just like the one for multiplying by 11.

We could create one, but why would we want one?

Example: 32 x 11...

Digit 1 = 3 x 1 = 3

Digit 3 = 2 x 1 = 2

Digit 2 = Digit 1 + Digit 3 = 5

Therefore 32 x 11 = 352

There is a lotmoreto the 11-rule . . .

What about 59 x 11 ?

The answer is 649 . . . How does your rule give that result?

To multiply 7856 times 11, append a zero to both ends: .

Starting at the right, add consecutivepairsof digits.

. . Perform the "carrying" as you work.

.

. - - - .

. . . Answer: .