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5 drill machines can drill 15 meters in 5 hours. [#permalink]
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ManishKM1 wrote:
5 drill machines can drill 15 meters in 5 hours. Assuming the speed of each machine to be the same, how many machines would be needed to drill 60 meters in 2 hours?

A)8
B)16
C)23
D)50
E)60

Find a machine's individual rate from the first information, and use it to solve the question.

W = (# of machines) * (indiv.) rate * time
W = 15, # of machines = 5, rate = ??, time = 5

15 = 5 * rate * 5
15 = 25 * rate

Individual rate = \(\frac{15}{25}=\frac{3}{5}\) in meters/hour

At that rate, how many machines are needed to drill 60 meters in 2 hours?

W = (# of machines) * (indiv.) rate * time
W = 60, # of machines = ??, rate = \(\frac{3}{5}\), time = 2

60 = (# of machines) * \(\frac{3}{5}\) * 2
60 = (# of machines) * \(\frac{6}{5}\)

# of machines = \(\frac{60}{(\frac{6}{5})}= 60 * \frac{5}{6}=\) 50

Answer D
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Re: 5 drill machines can drill 15 meters in 5 hours. [#permalink]
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ManishKM1 wrote:
5 drill machines can drill 15 meters in 5 hours. Assuming the speed of each machine to be the same, how many machines would be needed to drill 60 meters in 2 hours?

A)8
B)16
C)23
D)50
E)60


The rate for 5 drill machines is 15/5 = 3 meters per hour. We need to determine how many drill machines we need for a rate of 60/2 = 30 meters per hour. Since 30 is 10 times 3, we would need 5 x 10 = 50 drill machines.

Answer: D
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Re: 5 drill machines can drill 15 meters in 5 hours. [#permalink]
Expert Reply
\(\frac{(M_1 * H_1)}{W_1} = \frac{(M_2 * H_2)}{W_2}\\
\\
=> \frac{(5 * 5)}{ 15} = \frac{(M_2 * 2)}{ 60}\\
\\
=> M_2 = \frac{(5 * 5 * 60) }{ (15 * 2)}\\
\\
=> M_2 = 50\)

Answer D
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Re: 5 drill machines can drill 15 meters in 5 hours. [#permalink]
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