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# Last week, Rubi worked five days, from Monday to Friday inclusive. He

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Last week, Rubi worked five days, from Monday to Friday inclusive. He  [#permalink]

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06 Sep 2015, 09:36
1
2
00:00

Difficulty:

(N/A)

Question Stats:

74% (01:17) correct 26% (01:36) wrong based on 73 sessions

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Last week, Rubi worked five days, from Monday to Friday inclusive. He worked on average (arithmetic mean) 9 hours a day. On average, how many hours a day did he work during Monday and Tuesday?

(1) On average, Rubi worked 9 hours a day during Tuesday, Wednesday, Thursday and Friday.
(2) On average, Rubi worked 10 hours a day during Wednesday, Thursday and Friday.

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Re: Last week, Rubi worked five days, from Monday to Friday inclusive. He  [#permalink]

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06 Sep 2015, 16:14
1
IMO: B

Question Stem:

$$\frac{(M + T + W + Th + F )}{5} = 9$$
(M + T + W + Th + F ) = 45
$$\frac{(M + T )}{2} = ?$$

St 1: On average, Rubi worked 9 hours a day during Tuesday, Wednesday, Thursday and Friday.

$$\frac{( T + W + Th + F )}{4} = 9$$
Thus we get M = 9. Still T = ?
Hence not suff

St 2: On average, Rubi worked 10 hours a day during Wednesday, Thursday and Friday

$$\frac{( W + Th + F )}{3} = 10$$
( W + Th + F ) = 30
Thus M+T = 15
Hence suff
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Last week, Rubi worked five days, from Monday to Friday inclusive. He  [#permalink]

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07 Sep 2015, 06:26
Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and equations ensures a solution.

Last week, Rubi worked five days, from Monday to Friday inclusive. He worked on average (arithmetic mean) 9 hours a day. On average, how many hours a day did he work during Monday and Tuesday?

(1) On average, Rubi worked 9 hours a day during Tuesday, Wednesday, Thursday and Friday.
(2) On average, Rubi worked 10 hours a day during Wednesday, Thursday and Friday.

Monday:m, Tuesday:t, Wednesday:w, Thurday:h, Friday:f. transforming the original condition and the question, we have
m+t+w+h+f=9*5=45. since the question is asking for m+t, m+t=45-(w+h+f) thus we just need to know w+h+f.
Since from 2) we have w+h+f=10*3=30, the condition is sufficient. Therefore the answer is B.
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Re: Last week, Rubi worked five days, from Monday to Friday inclusive. He  [#permalink]

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15 Jul 2018, 01:41
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: Last week, Rubi worked five days, from Monday to Friday inclusive. He &nbs [#permalink] 15 Jul 2018, 01:41
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