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Jim can assemble b crates in an hour and Robert

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Jim can assemble b crates in an hour and Robert

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Jim can assemble b crates in an hour and Robert can assemble 2b crates in an hour. Working together at this rate, how many crates can they assemble in four hours?

A) 3b

B) 6b

C) 8b

D) 12b

E) 18b

The OA is D.

Which is the equation I should set to solve this PS question? Experts, may you give me some help, please?

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M7MBA wrote:
Jim can assemble b crates in an hour and Robert can assemble 2b crates in an hour. Working together at this rate, how many crates can they assemble in four hours?

A) 3b

B) 6b

C) 8b

D) 12b

E) 18b
We can also apply some logic to solve this question

Given: Jim can assemble b crates in 1 hour
So: Jim can assemble 2b crates in 2 hours [if we double the work time, we double the output]
So: Jim can assemble 4b crates in 4 hours [if we double the work time (again), we double the output]

Given: Robert can assemble 2b crates in 1 hour
So: Robert can assemble 4b crates in 2 hours [if we double the work time, we double the output]
So: Robert can assemble 8b crates in 4 hours [if we double the work time (again), we double the output]

So, when we COMBINE their efforts, we add their 4-hour OUTPUTS
That is, TOTAL output = color=red]4b[/color] + color=red]8b[/color] = 12b

Answer: D

Cheers,
Brent

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Quote:
Jim can assemble b crates in an hour and Robert can assemble 2b crates in an hour. Working together at this rate, how many crates can they assemble in four hours?

A) 3b

B) 6b

C) 8b

D) 12b

E) 18b

The OA is D.

Which is the equation I should set to solve this PS question? Experts, may you give me some help, please?
Hi M7MBA,
Let's take a look at your question.

$$\text{Jim's rate }\ =\ \frac{b}{1}=b$$
$$\text{Robert's rate}\ =\ \frac{2b}{1}=2b$$
$$\text{Jim and Robert's combined rate}\ = b+2b=3b$$

Working together number of crates they assemble in 1 hour = 3b
Working together number of crates they assemble in 4 hour = 3b * 4 = 12b

Therefore, Option D is correct.

Hope it helps.
I am available if you'd like any follow up.

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GMAT Prep From The Economist
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Hi M7MBA,

We're told that Jim can assemble B crates in an hour and Robert can assemble 2B crates in an hour. We're asked for the total number of crates that the two of them can assemble in four hours. This question can be solved Algebraically or by TESTing VALUES.

Using Algebra, you know the number of crates assembled by the two people in 1 hour (B+2B = 3B per hour). Thus, over 4 hours, you have (4)(3B) = 12B crates

TESTing VALUES, if... B = 2
Jim assembles 2 crates/hour
Robert assembles 4 crates/hour
Total = 6 crates an hour
In 4 hours.... (4)(6) = 24 crates are assembled.

Thus, we're looking for an answer that equals 24 when B=2. There's only one answer that matches.

Final Answer: D

GMAT assassins aren't born, they're made,
Rich

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Contact Rich at Rich.C@empowergmat.com

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