Joan collects rocks. In her collection of rock samples, she had half as many gemstones as minerals yesterday. Today, she went on a rock collecting trip and found 6 more mineral samples. If she has 48 minerals now, how many gemstone samples does she have?
Thoughts? Step-by-step reasoning:
Yesterday before her rock collecting trip, she had 48 - 6 = 42 mineral samples. She has 1 / 2 the number of gemstones, so she has 42 / 2 = 21 gemstone samples.
Thus, the answer is 21.