Multi-Step Ratio and Percent Problems Practice Test

A restaurant automatically adds an 18% gratuity to parties of 6 or more. If a party of 8 people has a bill of $240 before the gratuity, and they decide to leave an additional $15 cash tip, what is the total percent tip based on the original bill?

Simple interest is calculated using the formula $I = PRT$, where $P$ is principal, $R$ is annual rate, and $T$ is time in years. If $500 invested at 4.5% annual simple interest grows to $635 total, how many months was the money invested?