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Bunuel
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If Sabrina can assemble a tank in 8 hours, and Janis can assemble a ta 21 Jun 2018, 02:53
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D
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5% (low)

Question Stats:

89% (01:19) correct 11% (01:48) wrong based on 214 sessions

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If Sabrina can assemble a tank in 8 hours, and Janis can assemble a tank in 13 hours, then Sabrina and Janis working together at their constant respective rates can assemble a tank in approximately how many hours?

(A) 21
(B) 18
(C) 7
(D) 5
(E) 2
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D
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If Sabrina can assemble a tank in 8 hours, and Janis can assemble a ta 21 Jun 2018, 03:34
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Let's assume a certain number of 'units of work' that needs to be done. Best way is to take 8*13=104.

In such a case, each person's work rate is just the other person's hours required.

So Sabrina's work rate is 13 units/hour.
Janis' work rate is 8 units/hour.

Together, their work rate is 21 units per hour.

104/21 is closest to 5 (you can take 100/20 as an approximation).

Thus answer is D.
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If Sabrina can assemble a tank in 8 hours, and Janis can assemble a ta 21 Jun 2018, 07:46
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Solution



Given:

    • Sabrina can assemble a tank in 8 hours
    • Janis can assemble a tank in 13 hours

To find:
    • Sabrina and Janis, together can assemble a tank in how many hours.

Approach and Working:

    • Let the total work is of 104 units.
      o Then, Sabrina does 13 unit of work in 1 hour.
      o And Janis does 8 unit of work in 1 hour.
    • Together they will do 21 unit in 1 hour.
    • So to complete 104 units of work they will take104/21= approx. 5 hours.
Hence, the correct answer is option D.

Answer: D
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If Sabrina can assemble a tank in 8 hours, and Janis can assemble a ta 21 Jun 2018, 07:51
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IMO it is D.
8*13/(8+13) ~= 5
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If Sabrina can assemble a tank in 8 hours, and Janis can assemble a ta 24 Jun 2018, 17:58
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Bunuel
If Sabrina can assemble a tank in 8 hours, and Janis can assemble a tank in 13 hours, then Sabrina and Janis working together at their constant respective rates can assemble a tank in approximately how many hours?

(A) 21
(B) 18
(C) 7
(D) 5
(E) 2
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The combined rate of both women is 1/8 + 1/13 = 13/104 + 8/104 = 21/104, so the time is 1/(21/104) = 104/21 hours, or approximately 5 hours.

Answer: D
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If Sabrina can assemble a tank in 8 hours, and Janis can assemble a ta 30 Jun 2026, 12:36
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combined they are going to complete the task faster than Sabrina does alone, so A and B are out.

If two Sabrina's were working together, task would complete in half of Sabrina's time, so in 4 hours.

If two Janis's were working together, task would complete in half of Janis's time, so in 6.5 hours.

Hence when Sabrina and Janis are working together, there combined time to complete the task would fall somewhere b/w 4 hours and 6.5 hours. only option correct is D

by thinking logically, we can avoid numerical calculation entirely, the word 'approximately' is a clue to work your way through logic or estimation.
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If Sabrina can assemble a tank in 8 hours, and Janis can assemble a ta 30 Jun 2026, 15:50
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total unit=lcm(8,13)=104
s(rate)=13
j(rate)=8
hrs(s+j)=104/21=5
Bunuel
If Sabrina can assemble a tank in 8 hours, and Janis can assemble a tank in 13 hours, then Sabrina and Janis working together at their constant respective rates can assemble a tank in approximately how many hours?

(A) 21
(B) 18
(C) 7
(D) 5
(E) 2
Show more
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Bunuel
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