SOLUTION: Help!!! On the last day of class before Christmas break, Professor Morton brought donuts to his class that had been studying probability. "Before you get donuts, you must solve th

Algebra ->  Probability-and-statistics -> SOLUTION: Help!!! On the last day of class before Christmas break, Professor Morton brought donuts to his class that had been studying probability. "Before you get donuts, you must solve th      Log On


   

Question 472070: Help!!!
On the last day of class before Christmas break, Professor Morton brought donuts to his class that had been studying probability. "Before you get donuts, you must solve the following problem. I have a box of donuts that are either plain or chocolate covered. There are 12 chocolate-covered donuts, and the probability of randomly selecting a chocolate-covered donut is 0.6. How many donuts are in the box?" Find the number of donuts for the class.
Answer by Edwin McCravy(20086) About Me  (Show Source):
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Help!!!
On the last day of class before Christmas break, Professor Morton brought donuts to his class that had been studying probability. "Before you get donuts, you must solve the following problem. I have a box of donuts that are either plain or chocolate covered. There are 12 chocolate-covered donuts, and the probability of randomly selecting a chocolate-covered donut is 0.6. How many donuts are in the box?" Find the number of donuts for the class.
  12 = the number of chocolate donuts (given)
   x = the number of plain donuts
x+12 = the total number of donuts in the box

P(selecting a chocolate donut = %28NUMBER_OF_CHOCOLATE_DONUTS%29%2F%28TOTAL_NUMBER_OF_DONUTS%29 = 12%2F%28x%2B12%29+=+0.6

12%2F%28x%2B12%29+=+0.6

Multiply both sides by (x+12)

12+=+0.6%28x%2B12%29

Multiply both sides by 10

120+=+6%28x%2B12%29

120+=+6x%2B72

48+=+6x

8+=+x

So there were 12 chocolate donuts and 8 plain ones,
making 20 donuts for the class.

Edwin