Answer: $1 \cdot 2 \cdot 3 \cdot(4+5) \cdot 6 \cdot 7 \cdot 8: 9=2016$.
1. Can you use the four arithmetic operations (and also parentheses) to write the number 2016 using the digits 1, 2, 3, 4, 5, 6, 7, 8, 9 in sequence?