Pluggin math problems

[rycherx]

How can you tell if a math problem is a plug-in problem?
These problems always stump me.


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 4 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) (700m + nr)/100
c) m + nr
d) (7m + 100nr)/100
e) 700mnr

[kfree]

Originally posted by rycherx

How can you tell if a math problem is a plug-in problem?
These problems always stump me.


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 4 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) (700m + nr)/100
c) m + nr
d) (7m + 100nr)/100
e) 700mnr

(total cost) = (1 week maintain cost) + (1 week unit production cost)
(1 week maintain cost) = 7 days * (cost per day)
= 7 days * m dollars/day
= 7*m dollars
(1 week unit production cost) = 4 units * (cost per unit)
= 4 units * n cents/unit
= 4 units*n cents/unit*1/100 dollar/cents
= 4 * n * 1/100 dollars
(total cost) = (7*m + 4/100 * n ) dollars <-- move 100 out
= (7*100*m + 4 * n)/100 dollars

[yoyo]

answer choices do not make sense, unless I am missing something...

[Vinay]

the missing point here is variable r which is used instead of 4. but it doesnt matter coz answer is correct.

[sushilksood]

Rycherx: "How can you tell if a math problem is a plug-in problem?
These problems always stump me."

You can mostly use plug in when there is variable in the question and variables in the answer choices as well. Similar is true with percents i.e. when the question has everything in percent and answer choices are in %. This seems to work for me. Sushil