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BTGmoderatorDC wrote:Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of dough (with no chocolate) and 15 ounces of chocolate. How much chocolate is left over if he uses all the dough but only wants the cookies to consist of 20% chocolate?
(A) 3
(B) 6
(C) 7.2
(D) 7.8
(E) 9
Since chocolate must constitute 20% of the cookies, the 36 ounces of dough must constitute the remaining 80%:
36 = 0.8x
x = 36/0.8 = 360/8 = 45 ounces.
Since the cookies = 45 ounces, and the dough = 36 ounces, the amount of chocolate used = 45-36 = 9 ounces.
Thus -- of the 15 ounces of chocolate -- the amount left over = 15-9 = 6 ounces.
The correct answer is
B.
An alternate approach is to PLUG IN THE ANSWERS.
When the correct answer is plugged in, (chocolate used)/(chocolate used + dough) = 20% = 1/5.
Start with B or D.
Since B is an integer value, test B first.
B: 6 ounces of chocolate left over, implying that the amount of chocolate used = 9 ounces
In this case, (chocolate used)/(chocolate used + dough) = 9/(9+36) = 9/45 = 1/5.
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