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GRE Prep Club Legend  Joined: 07 Jun 2014
Posts: 4810
GRE 1: Q167 V156 WE: Business Development (Energy and Utilities)
Followers: 117

Kudos [?]: 1895 , given: 397

Jenny takes 3 hours to sand a picnic table; Laila can do the [#permalink]
Expert's post 00:00

Question Stats: 93% (00:54) correct 6% (00:00) wrong based on 16 sessions
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) $$\frac{5}{6}$$
[Reveal] Spoiler: OA

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Sandy
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Joined: 29 May 2018
Posts: 125
Followers: 0

Kudos [?]: 86  , given: 4

Re: Jenny takes 3 hours to sand a picnic table; Laila can do the [#permalink]
1
KUDOS
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) $$\frac{5}{6}$$

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.
GRE Prep Club Legend  Joined: 07 Jun 2014
Posts: 4810
GRE 1: Q167 V156 WE: Business Development (Energy and Utilities)
Followers: 117

Kudos [?]: 1895 , given: 397

Re: Jenny takes 3 hours to sand a picnic table; Laila can do the [#permalink]
Expert's post
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.

Attachment: image1.jpg [ 60.76 KiB | Viewed 481 times ]

Hence option D is correct!
_________________

Sandy
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Try our free Online GRE Test Re: Jenny takes 3 hours to sand a picnic table; Laila can do the   [#permalink] 10 Jul 2018, 05:41
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