Try the following GRE quantitative reasoning question that tests your understanding of how to set up mixtures and dilution questions.
Question#92:
The number of ounces of water needed to reduce $9$ ounces of shaving lotion containing $50\%$ alcohol to a lotion containing $30\%$ alcohol is:

$\quad 3$

$\quad 4$

$\quad 5$

$\quad 6$

$\quad 7$