A team of automotive machines have produced an average of 10 cars per

Question

A team of automotive machines have produced an average of 10 cars per day during the last 10 days. For how many days would the machines have to average 20 cars per day to raise the overall average to 12 cars per day?

(10*10+ 20*x)/(10+x) = 12
100+20x= 12(10+x)
100+ 20x = 120+12x
8x=20
x=20/8=2.5

Answer: B

A) 2
B) 2.5
C) 3
D) 3.5
E) 4

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APram · Answer

Let 20 cars be produced for x number of days

=> 20x + 10(10-x) = 12*10 = 120
=> 10x = 20
=> x = 2 days

Option A is correct.

ahmedrady · Answer

The answer is B,

for the average to be 12 you need the total number of produced cars divided by the total number of days to be 12.
Hence, (10*10+20*x)/(x+10)=12
10*10+20*x= 12(x+10)
By solving this equation x will yield 2.5

APram · Answer

I think the question has asked that the number of days be 10 as constant and out of those 10 days how many days 20 cars need to be produced so as to take the average to 12.

Correct me if I am wrong.

ahmedrady · Answer

IMO, They mentioned that they have already produced those cars in the  "last"  10 days and now they are looking to increase the average by increasing the cars/ day. 
They are not looking for an alternative scenario within the same 10 days.

Missinga · Answer

A team of automotive machines have produced an average of 10 cars per day during the last 10 days. For how many days would the machines have to average 20 cars per day to raise the overall average to 12 cars per day?

(10*10+ 20*x)/(10+x) = 12
100+20x= 12(10+x)
100+ 20x = 120+12x
8x=20
x=20/8=2.5

Answer: B

(10*10+ 20*x)/(10+x) = 12 
100+20x= 12(10+x)
100+ 20x = 120+12x 
8x=20
x=20/8=2.5

Answer: B

ManifestDreamMBA · Answer

Thinking logically, any day 20 cars are added, they have 8 extra from the average and compensates the deficit for 4 days.

We need to fix it for 10 days = 10/4 = 2.5days worth of 20cars/day avg required.

eb590 · Answer

The wording of the questions is tricky, shouldn't it say for how many MORE days?

Saying "For how many days would the machines have to average 20 cars per day to raise the overall average to 12 cars per day?" would mean we stick to the same 1o day period mentioned at the start of the question.

dolor · Answer

please explain this ans. thanks

Bunuel · Answer

There are several replies above. Have you checked those?

A team of automotive machines have produced an average of 10 cars per

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A team of automotive machines have produced an average of 10 cars per