math help

$ x=1
$ y=1.5
$ z=$((x*y))
bash: 1.5: syntax error: invalid arithmetic operator (error token is ".5")

What's wrong?

bash doesn't do floats. pipe your result to bc or do the math in awk

# echo "1*1.5" |bc
# awk 'BEGIN{print 1*1.5}' 

it worked
thanks alot