Doing math in bash is easy when you know how. Lets see...
some_number=$((10 * 100))
Done! The variable some_number
will produce 1,000. We done this by wrapping
our math in $(())
! Cool eh! What happens if you wanted to calculate something
first well it's just like using a sum formula in Excel
math=$(((10 * 100) + 100))
The above calculates the 10 * 100
first before adding the 100 to it.