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Jenny takes 3 hours to sand a picnic table; Laila can do the
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18 Jun 2018, 15:02
18 Jun 2018, 15:02
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Question Stats:
92% (00:57) correct
7% (01:26) wrong based on 57 sessions
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Jenny takes 3 hours to sand a picnic table; Laila can do the same job in \(\frac{1}{2}\) hour. Working together at their respective constant rates, Jenny and Laila can sand a picnic table in how many hours?
(A) \(\frac{1}{6}\)
(B) \(\frac{2}{9}\)
(C) \(\frac{1}{3}\)
(D) \(\frac{3}{7}\)
(E) \(\frac{5}{6}\)
(A) \(\frac{1}{6}\)
(B) \(\frac{2}{9}\)
(C) \(\frac{1}{3}\)
(D) \(\frac{3}{7}\)
(E) \(\frac{5}{6}\)
Re: Jenny takes 3 hours to sand a picnic table; Laila can do the
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19 Jun 2018, 06:03
19 Jun 2018, 06:03
1
sandy wrote:
Jenny takes 3 hours to sand a picnic table; Laila can do the same job in \(\frac{1}{2}\) hour. Working together at their respective constant rates, Jenny and Laila can sand a picnic table in how many hours?
(A) \(\frac{1}{6}\)
(B) \(\frac{2}{9}\)
(C) \(\frac{1}{3}\)
(D) \(\frac{3}{7}\)
(E) \(\frac{5}{6}\)
(A) \(\frac{1}{6}\)
(B) \(\frac{2}{9}\)
(C) \(\frac{1}{3}\)
(D) \(\frac{3}{7}\)
(E) \(\frac{5}{6}\)
Part of 1 hour work by Jenny = 1/3
Part of 1 hour work by Laila = 1 / 1/2 = 2.
Now part of 1 hour work by both = 1/3 + 2 = 7/3.
Now time inversely prop to work =? 3/7.
Re: Jenny takes 3 hours to sand a picnic table; Laila can do the
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10 Jul 2018, 05:41
10 Jul 2018, 05:41
Expert Reply
Explanation
Since the two women are working together, add their rates. To find their individual rates, divide work by time. Never divide time by work! (Also, be careful when dividing the work by \(\frac{1}{2}\).
The rate is the reciprocal of \(\frac{1}{2}\), or 2 tables per hour.)
Find Jenny and Laila’s combined rate, then divide the work required (1 table) by this rate: 1 table ÷ \(\frac{7}{3}\) table per hour = \(\frac{3}{7}\) hour.
image1.jpg [ 60.76 KiB | Viewed 5128 times ]
Hence option D is correct!
Since the two women are working together, add their rates. To find their individual rates, divide work by time. Never divide time by work! (Also, be careful when dividing the work by \(\frac{1}{2}\).
The rate is the reciprocal of \(\frac{1}{2}\), or 2 tables per hour.)
Find Jenny and Laila’s combined rate, then divide the work required (1 table) by this rate: 1 table ÷ \(\frac{7}{3}\) table per hour = \(\frac{3}{7}\) hour.
Attachment:
image1.jpg [ 60.76 KiB | Viewed 5128 times ]
Hence option D is correct!
