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Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of doug

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Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of doug [#permalink]

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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

Kudos for a correct solution.
[Reveal] Spoiler: OA

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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of doug [#permalink]

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New post 20 Apr 2015, 08:00
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Hi,
IMO is should be B
reason: Total new formed cookie contains 80% of dough only.
80% of 100 = 36
total cookie is of 45 ounce
20% of 45 is 9 ounce of chocolate.
hence 15-9 = 6 ounce of chocolate is left.

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Celestial


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Bunuel 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

Kudos for a correct solution.
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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of doug [#permalink]

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Bunuel 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

Kudos for a correct solution.


Let total weight of cookies = x

dough used = 36 ounces, which is 80% of the total

=> \(\frac{80}{100} *x = 36\) => x= 45 ounces

Out of 45 ounces, 20% is chocolate => \(\frac{20}{100}*45\) = 9 ounces

Thus, leftover chocolate = 15 - 9 = 6 ounces.

Hence, answer is B
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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of doug [#permalink]

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Bunuel 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

Kudos for a correct solution.


A common pitfall for a question like this would be to consider the 36 ounces of dough to be the total weight of the cookies which when taking 20% of gives you 7.2oz of chocolate used with 7.8 leftover giving us the trap answers found in C and D.

First, you must find the total weight of the mixture given that 80% of it will be dough. 80%*Total = 36 => (8/10)Total=36 => Total=360/8 => Total=45oz,

From there, you must find 20% of the total 45oz of the mixture. 20%*Total => (2/10)(45)= 9oz choclate used,

Not forgetting that the question asks how much chocolate is left over we must subtract the chocolate used from the initial chocolate. 15-9 = 6oz chocolate left over, select answer choice B.
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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of doug [#permalink]

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Bunuel 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

Kudos for a correct solution.



My answer choice is B, took me a little too long, but here is my process:

First I recognize that the answer choices indicate the exact amount of chocolate used by subtracting them from 15 ounces, so

A) 15-3left over = 12 ounces used 12+36= 48 --->48/12 gives 4, so 1/4 of the mixture is choc AKA 25%: too much!
B) 15-6left over= 9 ounces choc used 9+36 = 45 ---> 45/9 gives 5, so 1/5 of the mixture is choc AKA 20 % and this is the answer
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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of doug [#permalink]

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The ratio of chocolate : dough in the cookies is \(=\,20\%\,:\,80\%\) \(\,=\,1\,:\,4\)

Since uncle Bruce is using all of \(36\) ounces of dough, then the ratio of chocolate : dough is \(=\,9\,:36\,\)

So, the chocolate left unused is \(15\,-\,9\,=\,6\) ounces

Answer B
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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of doug [#permalink]

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New post 22 Apr 2015, 05:42
Bunuel 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

Kudos for a correct solution.



Dough/Chocolate = 80/20 = 4/1 => 4 parts = 36 => 1 part = 9
Therefore 15-9 = 6 remaining , answer is A
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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of doug [#permalink]

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New post 23 Apr 2015, 16:07
gamerssc wrote:
Bunuel 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

Kudos for a correct solution.



Dough/Chocolate = 80/20 = 4/1 => 4 parts = 36 => 1 part = 9
Therefore 15-9 = 6 remaining , answer is A


Hi gamerssc,

Your thinking in regards to this question is spot-on, but you still have to make sure that you're bubbling the correct answer on Test Day.

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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of doug [#permalink]

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Bunuel 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

Kudos for a correct solution.


VERITAS PREP OFFICIAL SOLUTION:

Now, we don’t want to gloss over the math here but there’s plenty of opportunity to practice with word problems and ratios in other posts and resources, so let’s cut to the true takeaway here. Most students will correctly arrive at the amount of chocolate used by employing a method similar to:

If the 36 ounces of dough are to be 80% of the total weight, then 36 = 4/5 * total.

That means that the total weight is 45 ounces, and so when we subtract out the 36 ounces of dough, there’s 9 ounces of chocolate in the cookies.

So…the answer is E. Right?

Wrong. Go back and double-check the question – the question asks for how much chocolate is LEFT OVER, not how much is USED. To be correct, you’d need to go back to the 15 original ounces of chocolate, subtract the 9 used, and correctly answer that 6 were left.

What’s the trap? GMAT questions are frequently set up so that you can answer the wrong question. If a question asks you to solve for y, it typically makes it easier to first solve for x…and then x is a trap answer. If a question asks you to strengthen a conclusion, the best way to weaken it is likely to be an answer choice. If a question asks for the maximum value, the minimum is going to be a trap.

The most common wrong answer to any problem on the GMAT is the right answer to the wrong question.

So take precaution – to avoid this trap, make sure that you:

Circle the variable for which you’re solving, or write down the question at the top of your work.

Jot a question mark at the top of your noteboard on test day, and tap it with your pen before you submit your answer to double check “did I answer the right question?”

Keep track of your units in word problems (minutes vs. seconds, amount used vs. amount remaining) and double check the units of your answer against the question
Make note of every time you make that mistake in practice, and as a more general tip be sure not to write off silly mistakes as just “silly mistakes”. If you made them in practice, you’re susceptible to them on the test, so make a note to watch out for them particularly if you’ve made the same mistake twice.
Few outcomes are more disappointing than doing all the work correctly but still getting the question wrong. The GMAT doesn’t do partial credit, so on a question like this falling for the trap is just as bad as not knowing how to get started. Get credit for what you know how to do – make sure you pause before you submit your answer to make sure that it answers the proper question!
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Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of dou [#permalink]

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Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of dough (with no chocolate) and 15 ounces of chocolate. How many ounces of chocolate are 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


Kudos for a correct solution.
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New to the Math Forum?
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Resources:
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Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of dou [#permalink]

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The cookies contain 20% chocolate and 80% dough.

Since all the dough is consumed, therefore 80% of total cookie mixture = 36 ounces

Therefore, Total mixture = 36*100/80 = 45 ounces.

Chocolate used = 45 - 36 = 9 ounces.

Left-over chocolate = 15 - 9 = 6 ounces

Ans- B
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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of dou [#permalink]

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Answer is B.

x/x+36=1/5
x=9

15-9=6
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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of dou [#permalink]

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Bunuel wrote:
Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of dough (with no chocolate) and 15 ounces of chocolate. How many ounces of chocolate are 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


Kudos for a correct solution.


20% chocolate means 80% must be donuts

i.e. 36 ounces = 80% of total Weight
i.e. 20% of total Weight = (36/80)*20 = 9 ounces

i.e. Chocolates Left-over = 15 - 9 = 6 Ounces

Answer: option B
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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of dou [#permalink]

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Bunuel wrote:
Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of dough (with no chocolate) and 15 ounces of chocolate. How many ounces of chocolate are 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


Kudos for a correct solution.

Solution : Let d and c be amounts of dough and chocolate used.
0.2(d+c)=c ==> c= d/4=9
Remaining = 15-9 = 6

Option B
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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of dou [#permalink]

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We have 36 ounces of dough and 15 ounces of chocolate.

We know the cookies consist of 20% chocolate.

so we are adding two weights, obviously the whole weight of the cookies is more: say x

so 80/100= 4/5 of x = 36

x = 45

amount of chocolate used = 45-36 = 9

15-9 = 6 ounces left

OA: B
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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of dou [#permalink]

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Bunuel wrote:
Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of dough (with no chocolate) and 15 ounces of chocolate. How many ounces of chocolate are 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


Kudos for a correct solution.


cookies contain 20 % chocolates and 80% dough.
So, the ratio of chocolate to dough is 1:4
Let the amount of chocolate use be x.
Then,
\(\frac{x}{36}\)=\(\frac{1}{4}\)
or x= 9

So, the amount of chocolate left is
15-9 = 6 ounces

Answer:- B
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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of dou [#permalink]

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New post 20 Sep 2015, 09:07
Bunuel wrote:
Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of dough (with no chocolate) and 15 ounces of chocolate. How many ounces of chocolate are 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


Kudos for a correct solution.


VERITAS PREP OFFICIAL SOLUTION:

Now, we don’t want to gloss over the math here but there’s plenty of opportunity to practice with word problems and ratios in other posts and resources, so let’s cut to the true takeaway here. Most students will correctly arrive at the amount of chocolate used by employing a method similar to:

If the 36 ounces of dough are to be 80% of the total weight, then 36 = 4/5 * total.

That means that the total weight is 45 ounces, and so when we subtract out the 36 ounces of dough, there’s 9 ounces of chocolate in the cookies.

So…the answer is E. Right?

Wrong. Go back and double-check the question – the question asks for how much chocolate is LEFT OVER, not how much is USED. To be correct, you’d need to go back to the 15 original ounces of chocolate, subtract the 9 used, and correctly answer that 6 were left.

What’s the trap? GMAT questions are frequently set up so that you can answer the wrong question. If a question asks you to solve for y, it typically makes it easier to first solve for x…and then x is a trap answer. If a question asks you to strengthen a conclusion, the best way to weaken it is likely to be an answer choice. If a question asks for the maximum value, the minimum is going to be a trap.

The most common wrong answer to any problem on the GMAT is the right answer to the wrong question.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of doug [#permalink]

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New post 20 Aug 2016, 19:38
let x=ounces of chocolate to be used
x=.2(36+x)=9 ounces
15-9=6 ounces
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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of doug [#permalink]

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Bunuel 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

Kudos for a correct solution.



We can use equivalent ratios.

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 leaves us with 6 ounces REMAINING.

Answer:
[Reveal] Spoiler:
B


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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of doug [#permalink]

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New post 18 Feb 2018, 13:01
Hi All,

This question can be solved in a couple of different ways. Here's an algebraic approach:

We're told to use 36 ounces of dough and enough chocolate (I'll refer to this amount as X ounces) so that the cookies are 20% CHOCOLATE. This is ultimately a ratio; the information can written in a couple of ways. Here's one...

Chocolate/All = X/(36+X) = 1/5

Now we can solve for X...

5X = 36 + X
4X = 36
X = 9

Thus, 9 ounces of chocolate are needed. Since we started with 15 ounces of chocolate, and the question asks how many ounces are LEFT OVER...

15 - 9 = 6 ounces left over.

Final Answer:
[Reveal] Spoiler:
B


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Re: Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of doug   [#permalink] 18 Feb 2018, 13:01
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Uncle Bruce is baking chocolate chip cookies. He has 36 ounces of doug

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