Number Theory
Number Theory Warmups
What is the last digit of
\[ 123 \times 321 ? \]
Hint: There is no need to completely multiply these numbers.
What is the last digit of
\[ 123 + 321 ? \]
What is the last digit of
\[ 1 \times 3 \times 5 \times 7 \times 9 ? \]
What is the last digit of
\[ 1 \times 2 \times 3 \times 4 \times 5 \times 6 \times 7 \times 8 \times 9 ? \]
What is the last digit of
\[ 1234 \times 5678 ? \]