You buy 30 of your favorite songs from a Web site that charges $0.98 for each song. What is the cost of 30 songs? Use mental math.

If you are going to use mental math, round $0.98 up to $1.

Rounded, the cost of the 30 songs is $30.

However, since you rounded at the beginning, you need to subtract 2 cents for every song you purchased from the total of $30.

Multiply 30 by $0.02 to get $0.60. Subtract $0.60 from $30.

Your answer should be $29.40.