Question 12
Find the units digit of A, where
$A=\underbrace{2\times2\times\cdots\times2}_{20}\times\underbrace{3\times3\times\cdots\times3}_{18}\times5$.
The braces show 20 factors of 2 and 18 factors of 3.
$A=\underbrace{2\times2\times\cdots\times2}_{20}\times\underbrace{3\times3\times\cdots\times3}_{18}\times5$.
The braces show 20 factors of 2 and 18 factors of 3.