Question

The total cost, including tax, of a $20 mouse for a personal computer is $21. What is the sales tax rate

Answer 1

Without tax it costs $20.
With tax it costs $21.
The amount of tax paid is $21 - $20 = $1

$1 tax was paid on $20.

$1/$20 * 100 = 0.05 * 100 = 5%