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A machine costs m dollars per day to maintain

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by canbtg » Sun May 11, 2014 2:53 am
A machine costs m dollars per day to maintain and n cents for each unit it produces. If the machine is operated 7 days a week and produces r units in a week, which of the following is the total cost, in dollars, of operating the machine for a week?


A)7m + 100nr

B)7m + nr / 100

c) 7m+nr

D)7m+100nr /100

E)700mnr

OA
B
Last edited by canbtg on Sun May 11, 2014 3:02 am, edited 1 time in total.
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by Brent@GMATPrepNow » Sun May 11, 2014 3:02 am
canbtg wrote:A colony of ants increases its population by 4 percent. If after this increase, bacteria deplete the population by , the new ant population is what percent of the original ant population?


A)16%


B)26%


C)29%


D)50%


E)78%
You're missing part of the question here.
We need to know the percent reduction caused by the bacteria.

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Brent
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by canbtg » Sun May 11, 2014 3:05 am
Brent@GMATPrepNow wrote:
canbtg wrote:A colony of ants increases its population by 4 percent. If after this increase, bacteria deplete the population by , the new ant population is what percent of the original ant population?


A)16%


B)26%


C)29%


D)50%


E)78%
You're missing part of the question here.
We need to know the percent reduction caused by the bacteria.

Cheers,
Brent
Hi Brent , Sincere apologies . I could solve the previous question , however , stuck at another one . So I just edited this post with a new question . Appreciate if you could help me to solve it.

Regards !
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by Brent@GMATPrepNow » Sun May 11, 2014 3:17 am
canbtg wrote:A machine costs m dollars per day to maintain and n cents for each unit it produces. If the machine is operated 7 days a week and produces r units in a week, which of the following is the total cost, in dollars, of operating the machine for a week?

A) 7m + 100nr
B) 7m + nr/ 100
C) 7m + nr
D) 7m + 100nr/100
E) 700mnr
TOTAL cost = maintenance cost + production cost

This machine costs m dollars per day to maintain, and the machine is operated 7 days.
So, the total maintenance cost = 7m dollars

The machine costs n CENTS for each unit it produces.
Since the question asks for the total cost in DOLLARS, we can convert n CENTS to n/100 DOLLARS
If the machine produces r units, then the total production cost = (n/100)(r) = rn/100 dollars

So, TOTAL cost = 7m + rn/100 dollars

Answer: B

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Brent
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by [email protected] » Sun May 11, 2014 1:47 pm
Hi canbtg,

This question can also be solved by TESTing VALUES.

We're told that there are 2 costs with running a machine:

M DOLLARS per day to maintain it
N CENTS per unit that it produces

We're told that R units are produced over the course of 7 days. We're asked for the cost, IN DOLLARS of operating the machine during that time.

Let's TEST VALUES:

M = 2
N = 3
R = 200

Over the course of 7 days, we spent ($2/day)(7 days) to maintain the machine and (3 cents)(200 units) on the units. Thus, we spent $14 + $6.00 = $20

The only answer that matches is B

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