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Math Expert V
Joined: 02 Sep 2009
Posts: 58453
Bob works exactly 8 hours per day assembling widgets at a constant rat  [#permalink]

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1 00:00

Difficulty:   5% (low)

Question Stats: 93% (00:51) correct 7% (01:08) wrong based on 131 sessions

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Bob works exactly 8 hours per day assembling widgets at a constant rate. How many widgets can he assemble in half of a workday?

(1) Bob produces 20 widgets in a full workday.

(2) Bob produces 50 widgets in 20 hours.

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Manager  Joined: 17 Oct 2015
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Location: India
Concentration: Finance
Schools: ISB '18 (S)
GMAT 1: 690 Q47 V37 GMAT 2: 700 Q44 V41 WE: Corporate Finance (Commercial Banking)
Re: Bob works exactly 8 hours per day assembling widgets at a constant rat  [#permalink]

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I think it is D. As both are sufficient.
Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8017
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Bob works exactly 8 hours per day assembling widgets at a constant rat  [#permalink]

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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 independent equations ensures a solution.

Bob works exactly 8 hours per day assembling widgets at a constant rate. How many widgets can he assemble in half of a workday?

(1) Bob produces 20 widgets in a full workday.
(2) Bob produces 50 widgets in 20 hours.

In the original condition, the question is the number of widgets Bob makes for 4 hours. So, you need to figure out power per hour, which makes 1 variable. In order to match with the number of equations, you need 1 equation. For 1) 1 equation, for 2) 1 equation, which is likely to make D the answer.
For 1), 10 widgets are made, which is unique and sufficient.
For 2), x=10 is derived from 50widgets:20hrs=x widgets:4hrs. Thus, 1)=2) and the answer is D.

 For cases where we need 1 more equation, such as original conditions with “1 variable”, or “2 variables and 1 equation”, or “3 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 59 % chance that D is the answer, while A or B has 38% chance and C or E has 3% chance. Since D is most likely to be the answer using 1) and 2) separately according to DS definition. Obviously there may be cases where the answer is A, B, C or E.
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Director  G
Joined: 09 Mar 2018
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Location: India
Re: Bob works exactly 8 hours per day assembling widgets at a constant rat  [#permalink]

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Work = Rate * time ( This formula we should remember)

Statement A: This alone is sufficient, As we know Bob produces 20 widgets in a full workday(8 hours).

By that information we can calculate how many widgets he will produce in half of a workday.

Statement 2: This alone is sufficient, As we know Bob produces 50 Widgets in 20 hours

By that information we can calculate how many widgets he will produce in 8 hours and then subsequently dividing our result in half, will give us a unique answer.

Since Both Statement 1 and Statement 2 are sufficient,

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Quote which i can relate to.
Many of life's failures happen with people who do not realize how close they were to success when they gave up. Re: Bob works exactly 8 hours per day assembling widgets at a constant rat   [#permalink] 17 Oct 2018, 10:42
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Bob works exactly 8 hours per day assembling widgets at a constant rat

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