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At Mindy's restaurant, for every 4 people who ordered cheesecake, ther 27 Oct 2021, 06:57
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35% (medium)

Question Stats:

64% (01:13) correct 36% (01:10) wrong based on 134 sessions

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At Mindy's restaurant, for every 4 people who ordered cheesecake, there are 5 people who ordered strudel. If we let C represent the number of cheesecakes ordered, and let S represent the number of strudels ordered, which of the following equations must be correct?

A) \(C + S = 9\)

B) \(4C = 5S\)

C) \(\frac{4}{9}S = C\)

D) \(4+C = 5+S\)

E) \(5C = 4S\)
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E
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At Mindy's restaurant, for every 4 people who ordered cheesecake, ther 28 Oct 2021, 06:28
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BrentGMATPrepNow
At Mindy's restaurant, for every 4 people who ordered cheesecake, there are 5 people who ordered strudel. If we let C represent the number of cheesecakes ordered, and let S represent the number of strudels ordered, which of the following equations must be correct?

A) \(C + S = 9\)

B) \(4C = 5S\)

C) \(\frac{4}{9}S = C\)

D) \(4+C = 5+S\)

E) \(5C = 4S\)
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Note: This question is from a popular study in mathematics education research: https://www.jstor.org/stable/748434
In the study, this question was posed to 150 first-year engineering students, and only 27% of the students were able to correctly answer it.

Given: For every 4 people who ordered cheesecake, there are 5 people who ordered strudel
In other words: (The number of cheesecake people)/(The number of strudel people) = 4/5
Substitute variables to get: C/S = 4/5
Cross multiply to get: 5C =4S

Answer: E

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At Mindy's restaurant, for every 4 people who ordered cheesecake, ther 21 Nov 2021, 12:34
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BrentGMATPrepNow
BrentGMATPrepNow
At Mindy's restaurant, for every 4 people who ordered cheesecake, there are 5 people who ordered strudel. If we let C represent the number of cheesecakes ordered, and let S represent the number of strudels ordered, which of the following equations must be correct?

A) \(C + S = 9\)

B) \(4C = 5S\)

C) \(\frac{4}{9}S = C\)

D) \(4+C = 5+S\)

E) \(5C = 4S\)

Note: This question is from a popular study in mathematics education research: https://www.jstor.org/stable/748434
In the study, this question was posed to 150 first-year engineering students, and only 27% of the students were able to correctly answer it.

Given: For every 4 people who ordered cheesecake, there are 5 people who ordered strudel
In other words: (The number of cheesecake people)/(The number of strudel people) = 4/5
Substitute variables to get: C/S = 4/5
Cross multiply to get: 5C =4S

Answer: E

RELATED VIDEO
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Why is B incorrect? C:S:Total = 4:5:9 so 4C=5S. I am just curious because I want to avoid careless mistakes next time.

Thanks!
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At Mindy's restaurant, for every 4 people who ordered cheesecake, ther 21 Nov 2021, 13:13
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BrentGMATPrepNow
BrentGMATPrepNow
At Mindy's restaurant, for every 4 people who ordered cheesecake, there are 5 people who ordered strudel. If we let C represent the number of cheesecakes ordered, and let S represent the number of strudels ordered, which of the following equations must be correct?

A) \(C + S = 9\)

B) \(4C = 5S\)

C) \(\frac{4}{9}S = C\)

D) \(4+C = 5+S\)

E) \(5C = 4S\)

Note: This question is from a popular study in mathematics education research: https://www.jstor.org/stable/748434
In the study, this question was posed to 150 first-year engineering students, and only 27% of the students were able to correctly answer it.

Given: For every 4 people who ordered cheesecake, there are 5 people who ordered strudel
In other words: (The number of cheesecake people)/(The number of strudel people) = 4/5
Substitute variables to get: C/S = 4/5
Cross multiply to get: 5C =4S

Answer: E

RELATED VIDEO

Why is B incorrect? C:S:Total = 4:5:9 so 4C=5S. I am just curious because I want to avoid careless mistakes next time.

Thanks!
Show more

You're correct to say that C:S = 4:5, but keep in mind that we are equating two ratios, whereas the equation 4C=5S equates two values

Notice that, if C:S = 4:5, then it could be the case that C = 8 and S = 10 (since 8:10 = 4:5)
Now let's test whether the equation 4C=5S holds true with these two values.
Substitute to get: 4(8) = 5(10)
Simplify: 32 = 50
So, the correct answer can't be true.

However, when we plug these values (C = 8 and S = 10) and to answer choice E, we get: 5(8) = 4(10), which simplifies to be 40 = 40 (perfect!)

Does that help?
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At Mindy's restaurant, for every 4 people who ordered cheesecake, ther 21 Nov 2021, 15:10
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BrentGMATPrepNow ,


It does yes. For next time I am solving a problem like that, is there anything that can help me realize that while the ratio is, for instance 4:5, the values are actually 5C = 4S - without having to make all of these calculations? In other words, I would like to improve my conceptual thinking here I guess.

Thanks!
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At Mindy's restaurant, for every 4 people who ordered cheesecake, ther 21 Nov 2021, 15:35
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BrentGMATPrepNow ,


It does yes. For next time I am solving a problem like that, is there anything that can help me realize that while the ratio is, for instance 4:5, the values are actually 5C = 4S - without having to make all of these calculations? In other words, I would like to improve my conceptual thinking here I guess.

Thanks!
Show more

In the future, I suggest that, when you must translate a word problem involving ratios, use fraction notation to first express the relationship.
For example, if you're told that the ratio of x to y is 2 to 3, you can first write: x/y = 2/3
Then cross multiply to get: 3x = 2y

In general, If the ratio of x to y is m to k, then we can first write: x/y = m/k
Then cross multiply to get: kx = my
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