Miruna had to multiply two $$2$$-digit numbers together, but she accidentally reversed the digits of both of them before multiplying and reached the answer $$209$$. Which of the following answers should she have obtained? 
Overseas Competition->Knowledge Point->Counting Modules->Permutations and Combinations->Combinations
The prime factors of $$209$$ are $$11$$ and $$19$$, so these must have been the reversed numbers that Miruna multiplied. The correct multiplication was $$11 \times 91=1001$$. 