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Ryerson (Ted Rogers) Thread Master
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Re: Working at their respective constant rates, machine A makes 100 copies [#permalink]
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RSOHAL wrote:
Working at their respective constant rates, machine A makes 100 copies in 12 minutes and machine B makes 150 copies in 10 minutes. If these machines work simultaneously at their respective rates for 30 minutes, what is the total number of copies that they will produce?

(A) 250
(B) 425
(C) 675
(D) 700
(E) 750


Machine A can produce 100 *30/12= 250 copies

And, Machine B can produce 150* 30/10= 450 Copies

Total producing 700 Copies.

D is the answer
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Re: Working at their respective constant rates, machine A makes 100 copies [#permalink]
RSOHAL wrote:
Working at their respective constant rates, machine A makes 100 copies in 12 minutes and machine B makes 150 copies in 10 minutes. If these machines work simultaneously at their respective rates for 30 minutes, what is the total number of copies that they will produce?

(A) 250
(B) 425
(C) 675
(D) 700
(E) 750


A makes in 12 min 100 copies..so in 1 min it makes 25/3 copies
B makes in 10 min 150 copies..so in 1 min it makes 15 copies

So working together A+B in 1 min makes = 25/3+15 = 70/3 copies

So in 30 min they will make = 30*70/3=700 copies so ans is D
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Re: Working at their respective constant rates, machine A makes 100 copies [#permalink]
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This is a simple question on the concept of Rates.

From the first statement in the question, we can find out the respective rates at which the machines work. Then, we can multiply the rate values with the time to obtain the total work done.

So, the only equation/formula that you need to solve this question is the equation,

Work = Rate * Time

Modifying the above can give us the equation for rate as Rate = \(\frac{Work }{ Time}\).

Rate at which machine A copies = \(\frac{100 }{ 12}\) copies per minute

Rate at which machine B copies = \(\frac{150 }{ 10}\) = 15 copies per minute.

Now, we have been told that each of these machines work independently for 30 minutes; therefore, time = 30 minutes. The number of copies produced by each machine will represent the work done by that machine.

Number of copies produced by machine A = Rate of machine A * Time = \(\frac{100 }{ 12 }\)* 30 = 250

Number of copies produced by machine B = Rate of machine B * Time = 15 * 30 = 450

Therefore, total copies produced by the two machines = 250 + 450 = 700.

The correct answer option is D.
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Working at their respective constant rates, machine A makes 100 copies [#permalink]
12 mins 100 copies i.e 60 mins 500 copies
10 mins 150 copies i.e 60 mins 900 copies

i.e 60 mins 1400 copies
i.e 30 mins 700 copies
Option E
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Re: Working at their respective constant rates, machine A makes 100 copies [#permalink]
Expert Reply
RSOHAL wrote:
Working at their respective constant rates, machine A makes 100 copies in 12 minutes and machine B makes 150 copies in 10 minutes. If these machines work simultaneously at their respective rates for 30 minutes, what is the total number of copies that they will produce?

(A) 250
(B) 425
(C) 675
(D) 700
(E) 750


I don't like fractional rates and prefer working with easy time parts.

A makes 100 in 12 minutes, so 500 per hour.
B makes 150 in 10 minutes, so 900 per hour.
Together they make 1400 per hour.
So in a half hour, they make 700.

Answer choice D.
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Re: Working at their respective constant rates, machine A makes 100 copies [#permalink]
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Re: Working at their respective constant rates, machine A makes 100 copies [#permalink]
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