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At a loading dock.. Need expert help!

by Elena89 » Mon Dec 12, 2011 4:02 am
At a loading dock, each worker on the night crew loaded 3/4 as many boxes as each worker on the day crew. If the night crew has 4/5 as many workers as the day crew, what fraction of all the boxes loaded by the two crews did the day crew load?

(A) 1/2

(B) 2/5

(C) 3/5

(D) 4/5

(E) 5/8

Source: OG-12
[spoiler]OA (E) And I dont understand how. Can someone please guide?[/spoiler]
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by Anurag@Gurome » Mon Dec 12, 2011 4:07 am
Elena89 wrote:At a loading dock, each worker on the night crew loaded 3/4 as many boxes as each worker on the day crew. If the night crew has 4/5 as many workers as the day crew, what fraction of all the boxes loaded by the two crews did the day crew load?

(A) 1/2

(B) 2/5

(C) 3/5

(D) 4/5

(E) 5/8

Source: OG-12
[spoiler]OA (E) And I dont understand how. Can someone please guide?[/spoiler]
Say, number of workers in the day crew = w
=> Number of workers in the night crew = 4w/5.

Say, total number of boxes loaded by the day crew = x
=> Number of boxes loaded by each of the workers in the day crew = x/w.
=> Number of boxes loaded by each of the workers in the night crew = (3/4)*(x/w).
=> Total number of boxes loaded by the night crew = Number of workers in the night crew * Boxes loaded by each of the workers in the night crew = (4w/5)*[(3/4)*(x/w)] = 3x/5.

Therefore, total number of boxes loaded by the two crews = Boxes loaded by the day crew + Boxes loaded by the night crew = x + 3x/5 = 8x/5.

Therefore, required fraction = Boxes loaded by the day crew/Total number of boxes loaded by the two crews = x/(8x/5) = 5/8.

The correct answer is E.
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by GMATGuruNY » Mon Dec 12, 2011 4:46 am
Elena89 wrote:At a loading dock, each worker on the night crew loaded 3/4 as many boxes as each worker on the day crew. If the night crew has 4/5 as many workers as the day crew, what fraction of all the boxes loaded by the two crews did the day crew load?

(A) 1/2

(B) 2/5

(C) 3/5

(D) 4/5

(E) 5/8

Source: OG-12
[spoiler]OA (E) And I dont understand how. Can someone please guide?[/spoiler]
Day crew:
Let the number of workers = 5.
Let the number of boxes loaded by each worker = 4.
Total number of boxes loaded = 5*4 = 20.

Night crew:
Since the night crew has 4/5 as many workers as the day crew, the number of workers on the night crew = (4/5)5 = 4.
Since each worker on the night crew loaded 3/4 as many boxes as each worker on the day crew, the number of boxes loaded by each night crew worker = (3/4)4 = 3.
Total number of boxes loaded = 4*3 = 12.

(Boxes loaded by the day crew)/(Total number of boxes loaded by the two crews) = 20/(20+12) = 20/32 = 5/8.

The correct answer is E.
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by batmannavneet » Mon Dec 12, 2011 5:04 am
Let D (Day) rate = 4 units, which means N (night) rate = 3 units
Let D workers = 5, which means N works = 4

Therefore, answer = 5*4/(5*4 + 3*4) = 20/32 = 5/8 = Pick E
Elena89 wrote:At a loading dock, each worker on the night crew loaded 3/4 as many boxes as each worker on the day crew. If the night crew has 4/5 as many workers as the day crew, what fraction of all the boxes loaded by the two crews did the day crew load?

(A) 1/2

(B) 2/5

(C) 3/5

(D) 4/5

(E) 5/8

Source: OG-12
[spoiler]OA (E) And I dont understand how. Can someone please guide?[/spoiler]
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by Castor.kim » Mon Sep 10, 2012 6:31 pm
Dear masters of GMAT,

I can't understand why 'two crews' mean that "both crew, day and night"?
may it could be mean that 2 number of day crew or 2 number of night crew?

actually, I failed this problem because that I solve
"Box loaded by day crew / (Box loaded by night crew * 2)"
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by Brent@GMATPrepNow » Mon Sep 10, 2012 9:16 pm
Elena89 wrote:At a loading dock, each worker on the night crew loaded 3/4 as many boxes as each worker on the day crew. If the night crew has 4/5 as many workers as the day crew, what fraction of all the boxes loaded by the two crews did the day crew load?

(A) 1/2

(B) 2/5

(C) 3/5

(D) 4/5

(E) 5/8

Source: OG-12
[spoiler]OA (E) And I dont understand how. Can someone please guide?[/spoiler]
I think the fast way is to plug in some nice numbers.
Since the two pieces of information regarding the night shift are related to the information regarding the day shift, let's assign some nice values to the day shift.

Number of workers
Day shift: 5 workers (this is an easy number to find 4/5 of)
Night shift: 4 workers (4/5 of 5 = 4)

Boxes loaded per worker
Day shift: 4 boxes per worker
Night shift: 3 boxes per worker (3/4 of 4 = 3)

Total boxes loaded
Day shift: 5 workers times 4 boxes per worker = 20 boxes
Night shift: 4 workers times 3 boxes per worker = 12 boxes

Combined total boxes for both shifts = 20 + 12 = 32

Of the 32 boxes, the day shift loaded 20 of them.
20/32 = 5/8 = E

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Brent
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