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# Machine A, working alone at its constant rate, manufactures 280 bolts

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Math Expert
Joined: 02 Sep 2009
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Machine A, working alone at its constant rate, manufactures 280 bolts  [#permalink]

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05 Jul 2018, 01:43
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Difficulty:

5% (low)

Question Stats:

91% (01:05) correct 9% (02:18) wrong based on 112 sessions

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Machine A, working alone at its constant rate, manufactures 280 bolts per hour, and machine B, working alone at its constant rate, manufactures 220 bolts per hour. How many hours will it take for machines A and B, working together at their respective constant rates,to manufacture 1,000 bolts?

A. 1
B. 1.3
C. 1.5
D. 1.8
E. 2

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Re: Machine A, working alone at its constant rate, manufactures 280 bolts  [#permalink]

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05 Jul 2018, 01:51
2
Bunuel wrote:
Machine A, working alone at its constant rate, manufactures 280 bolts per hour, and machine B, working alone at its constant rate, manufactures 220 bolts per hour. How many hours will it take for machines A and B, working together at their respective constant rates,to manufacture 1,000 bolts?

A. 1
B. 1.3
C. 1.5
D. 1.8
E. 2

In 1 hour A and B will make 220+280 bolts. Thus, in one hour total of 500 bolts are produced.

For 1000 bolts, 2 hours would be required.

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Machine A, working alone at its constant rate, manufactures 280 bolts  [#permalink]

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05 Jul 2018, 06:17
Bunuel wrote:
Machine A, working alone at its constant rate, manufactures 280 bolts per hour, and machine B, working alone at its constant rate, manufactures 220 bolts per hour. How many hours will it take for machines A and B, working together at their respective constant rates,to manufacture 1,000 bolts?

A. 1
B. 1.3
C. 1.5
D. 1.8
E. 2

Rate of manufacturing of machine A=280 bolts per hour
Rate of manufacturing of machine B=220 bolts per hour

Combined rate*time=Work done
or, (280+220)bolt/hour*time=1000 bolts
Or, Time=$$\frac{1000}{500}$$=2 hours

Ans. E
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Re: Machine A, working alone at its constant rate, manufactures 280 bolts  [#permalink]

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05 Jul 2018, 07:26
Bunuel wrote:
Machine A, working alone at its constant rate, manufactures 280 bolts per hour, and machine B, working alone at its constant rate, manufactures 220 bolts per hour. How many hours will it take for machines A and B, working together at their respective constant rates,to manufacture 1,000 bolts?

A. 1
B. 1.3
C. 1.5
D. 1.8
E. 2

Since the efficiency of both the machines are given it boils down to -

$$\frac{1000}{(220 + 280)} = 2$$ Hours, Answer must be (E)
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Re: Machine A, working alone at its constant rate, manufactures 280 bolts  [#permalink]

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07 Jul 2018, 18:31
Bunuel wrote:
Machine A, working alone at its constant rate, manufactures 280 bolts per hour, and machine B, working alone at its constant rate, manufactures 220 bolts per hour. How many hours will it take for machines A and B, working together at their respective constant rates,to manufacture 1,000 bolts?

A. 1
B. 1.3
C. 1.5
D. 1.8
E. 2

Since the combined rate is 500 bolts per hour, then it will take 1,000/500 = 2 hours for the two machines to manufacture 1,000 bolts.

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Re: Machine A, working alone at its constant rate, manufactures 280 bolts  [#permalink]

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02 Oct 2018, 06:15
In one hour total bolts made=280+220=>500 bolts
500 bolts in 1 hr
So, 1000 bolts in 2 hrs.
(E)
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Re: Machine A, working alone at its constant rate, manufactures 280 bolts  [#permalink]

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09 Oct 2019, 02:01
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Re: Machine A, working alone at its constant rate, manufactures 280 bolts   [#permalink] 09 Oct 2019, 02:01
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