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
OA B
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Uncle Bruce is baking chocolate chip cookies. He has 36
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BTGmoderatorDC
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=
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.
Success!
Since chocolate must constitute 20% of the cookies, the 36 ounces of dough must constitute the remaining 80%: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
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.
Success!
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We can also use equivalent ratiosBTGmoderatorDC 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
The cookies will consist of 20% chocolate.
In other words, the cookies will consist of 1/5 chocolate.
We can also say the cookies will consist of 4/5 dough.
This means the cookies are 4 parts dough and 1 part chocolate.
So, the dough to chocolate ratio = 4/1
We have 36 ounces of dough available.
Let c = the number of ounces of chocolate needed.
We now can use equivalent ratios to set up the equation: 4/1 = 36/c
Solve to get c = 9
So, we need to USE 9 ounces of chocolate, which leave us with 6 ounces REMAINING.
Answer: B
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Scott@TargetTestPrep
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Let x = the amount of chocolate to be used so that the cookies consist of 20% chocolate. We have: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
OA B
Source: Veritas Prep
x/(36 + x) = 20/100
x/(36 + x) = 1/5
5x = 36 + x
4x = 36
x = 9
Thus, if the cookies are to contain 20% chocolate, 15 - 9 = 6 ounces of chocolate will remain.
Answer: B
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