Question 983999
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(18/120)(100%)=15%
The black jelly beans should be about 15% of the total.
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(90/0.15)=600 
90 black beans are 15% of 600 jelly beans.
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600 total jelly beans-90 added black jelly beans=510 original jelly beans
Subtract the 90 added black jelly beans to find the original number.
ANSWER: There were originally 510 jelly beans, so (B) is correct.