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Mariko can knit 5 rows of a scarf in x minutes. If there are

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Mariko can knit 5 rows of a scarf in x minutes. If there are [#permalink]  31 May 2017, 07:16
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Question Stats:

66% (02:20) correct 33% (01:56) wrong based on 6 sessions
Mariko can knit 5 rows of a scarf in x minutes. If there are 100 rows in each foot of the scarf, how many hours, in terms of x and y, will it take Mariko to finish a scarf that is y feet long?

A. $$\frac{xy}{3}$$
B. $$\frac{1200}{xy}$$
C. $$1200xy$$
D. $$\frac{3}{xy}$$
E. $$3xy$$

Drill 2
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[Reveal] Spoiler: OA

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Sandy
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GRE Prep Club Legend
Joined: 07 Jun 2014
Posts: 4856
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 102

Kudos [?]: 1737 [1] , given: 397

Re: Mariko can knit 5 rows of a scarf in x minutes. If there are [#permalink]  02 Jul 2017, 14:53
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Explanation

As soon as you see variables in the answer choices, set up your scratch paper to Plug In.

Start with x = 5, so it takes 1 minute to knit 1 row. Now make y = 2. A scarf 2 feet long means Mariko has to knit 200 rows, which will take 200 minutes; since the problem asks how many hours it will take, your target answer is $$\frac{200}{60}=3\frac{1}{3}$$.

Now plug your values into the answer choices; only choice (A) hits your target. Choices (C) and (E) are clearly too small, and choice (D) is a fraction, so you may not have to calculate all the choices.

Hence option A is correct!
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Re: Mariko can knit 5 rows of a scarf in x minutes. If there are [#permalink]  16 Sep 2017, 23:33
Is it a typo the fact that there is a z instead of y?
GRE Prep Club Legend
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Re: Mariko can knit 5 rows of a scarf in x minutes. If there are [#permalink]  17 Sep 2017, 04:19
Expert's post
IlCreatore wrote:
Is it a typo the fact that there is a z instead of y?

Fixed it!
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Re: Mariko can knit 5 rows of a scarf in x minutes. If there are [#permalink]  06 Dec 2017, 16:34
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Another alternative solution would be to translate the question into an equation:

Hourly rate of rows: (5/x)*60
Total rows needed: 100y

Time required for 100y rows = 100y/((5/x)*60) => 100Y/(300/x) => 100yx/300 => YX/3
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Re: Mariko can knit 5 rows of a scarf in x minutes. If there are [#permalink]  09 May 2018, 15:05
Expert's post
[quote="sandy"]Mariko can knit 5 rows of a scarf in x minutes. If there are 100 rows in each foot of the scarf, how many hours, in terms of x and y, will it take Mariko to finish a scarf that is y feet long?

A. $$\frac{xy}{3}$$
B. $$\frac{1200}{xy}$$
C. $$1200xy$$
D. $$\frac{3}{xy}$$
E. $$3xy$$ /quote]

Since the scarf is y feet, there are 100y rows.

Since Mariko’s rate is 5/x, it will take him 100y/(5/x) = 100xy/5 = 20xy minutes or 20xy/60 = xy/3 hours.

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Re: Mariko can knit 5 rows of a scarf in x minutes. If there are   [#permalink] 09 May 2018, 15:05
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