Question 19
The operator $\otimes$ acts on two numbers as follows:
$$2\otimes6=44,\quad4\otimes10=87,$$
$$8\otimes18=1613,\quad16\otimes22=2019.$$
Find $7\otimes9$.
Pattern convention: finitely many examples do not uniquely define an operator. This source puzzle is graded using the published intended arithmetic-and-digit-concatenation pattern; other rules are mathematically possible.
Answer format: enter one whole number without units; leading zeros are optional. The source answer sheet uses four digits (for example, 7 is shaded as 0007).
$$2\otimes6=44,\quad4\otimes10=87,$$
$$8\otimes18=1613,\quad16\otimes22=2019.$$
Find $7\otimes9$.
Pattern convention: finitely many examples do not uniquely define an operator. This source puzzle is graded using the published intended arithmetic-and-digit-concatenation pattern; other rules are mathematically possible.
Answer format: enter one whole number without units; leading zeros are optional. The source answer sheet uses four digits (for example, 7 is shaded as 0007).