Mariko can knit 5 rows of a scarf in x minutes. If there are 100 rows

Question

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

SSM700plus · Accepted Answer

1 foot has 100 rows .

For y feet long will have 100y rows.

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

For 100 rows. He will take 20x minutes.

For 100y rows. He will take 20xy minutes.

Question has been asked to find out the time taken in hours.
Hence 20xy/60.

Ans is xy/3.

Hence A

EgmatQuantExpert · Answer

Solution

Given:  
• Mariko can knit 5 rows of a scarf in x minutes
 o Therefore, Mariko can knit 1 row in  \frac{x}{5}  minutes 
• There are 100 rows in each foot of the scarf

To find:  
• How many hours, in terms of x and y, will Mariko take to finish a y-feet long scarf

Approach and Working:   
• In the scarf, total number of rows = 100 * y = 100y
 o If 1 row takes  \frac{x}{5}  minutes to knit, then 100y rows will take  \frac{x}{5}  * 100y minutes 
 Or, 20xy minutes  
 Or,  \frac{20xy}{60} hrs = \frac{xy}{3}  hrs

Hence, the correct answer is option A.

Answer: A

generis · Answer

Assign values 
Let  x  minutes' value = a factor of  60  (we have minutes and know we need hours). Change the rate to rows per HOUR. Then assign a value to  y

Let  x  minutes = 10 
 Change the rate to hours* 
  \frac{5rows}{10mins}=\frac{30rows}{60mins}=\frac{30rows}{1hour}

We have two values, 30 and 100, to deal with. So let  y=3  feet

How much work?
  W=(\frac{100rows}{1foot}* 3 feet)= 300rows

Time to finish that work? 300 rows, at 30 rows per hour, will require 10 hours to finish

Use  x=10, y=3 . Find the answer choice that yields  10

Eliminate C and E immediately. Both are huge.

A.  \frac{xy}{3} :  \frac{10*3}{3}=10  KEEP

B.  \frac{1200}{xy} :  \frac{1200}{10*3}=40  REJECT

D.  \frac{3}{xy} :  \frac{3}{10*3}=\frac{1}{10}  REJECT

Answer A

*To convert from minutes to hours: 1) write rate in minutes; 2) find rate in 60 minutes; and 3) change the denominator to "1 hour" but leave the numerator alone. The step in which minutes cancel has simply been omitted:

\(\frac{5rows}{10mins}=\frac{30rows}{60mins}*(\frac{60mins}{1hour})=\frac{30rows}{1hour}\)

\frac{5rows}{10mins}=\frac{30rows}{60mins}*(\frac{60mins}{1hour})=\frac{30rows}{1hour}

Basshead · Answer

We're told: Mariko can knit 5 rows of a scarf in x minutes.

Mariko's rate: 1 row in x/5 minutes.

There are 100 rows in each foot of the scarf.

100 rows = x/5 * 100 = 100x/5 =  20x minutes .

How many hours will it take Mariko to finish a scarf that is y feet long? The keyword here is  hours . In the question prompt we were given a value in minutes.

Thus:

20x minutes * y = 20xy

20xy / 60 =  xy / 3

Answer is A.

bumpbot · Answer

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Mariko can knit 5 rows of a scarf in x minutes. If there are 100 rows

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Mariko can knit 5 rows of a scarf in x minutes. If there are 100 rows

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