Barite is well-known for its great range of colors and varied crystal forms and habits. It is an immensely popular mineral among collectors. A chemist is investigating a new reaction to synthesize barite crystals. She finds that eight grams are synthesized every five minutes. If there are 111 grams of barite after an hour, how many grams of barite did the chemist start with?
Answer is C.
There are 12 five minutes intervals in an hour (60/5). So there are 8 x 12 = 96 crystals after an hour. Since there are 111 crystals, she must have started with 111-96, which is 15 crystals.
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