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A group of ten candy bars has an average cost of $0.89 per c
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21 Mar 2019, 05:09
21 Mar 2019, 05:09
Expert Reply
00:00
Question Stats:
83% (01:25) correct
16% (00:52) wrong based on 6 sessions
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A group of ten candy bars has an average cost of $0.89 per candy bar. How many additional bars must be bought at the cost of $0.72 a piece to bring the average down to $0.80?
Show: :: OA
12
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Re: A group of ten candy bars has an average cost of $0.89 per c
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24 Mar 2019, 08:15
24 Mar 2019, 08:15
3
Carcass wrote:
A group of ten candy bars has an average cost of $0.89 per candy bar. How many additional bars must be bought at the cost of $0.72 a piece to bring the average down to $0.80?
Show: :: OA
12
10 candy bars have an average cost of $0.89
So, COST of those 10 candy bars = (10)($0.89) = $8.90
Let x = the NUMBER of $0.72 candy bars needed
So, 0.72x = the COST of those x EXTRA candy bars
When we add x candy bars to the existing 10 candy bars, we get a TOTAL of 10 + x candy bars
We want the average cost to be $0.80
We want: (total COST of all candy bars)/(NUMBER of candy bars) = $0.80
Rewrite as: ($8.90 + 0.72x)/(10 + x) = 0.80
Multiply both sides by (10 + x) to get: ($8.90 + 0.72x) = 0.80(10 + x)
Simplify right side to get: 8.90 + 0.72x = 8 + 0.8x
Subtract 0.72x from both sides to get: 8.90 = 8 + 0.08x
Subtract 8 from both sides to get: 0.90 = 0.08x
Solve to get: x = 0.90/0.08 = 11.25
Hmmmm, I don't like this question.
Presumably, the correct answer is 12 because this would bring the average cost BELOW $0.80
However, the question doesn't say BELOW $0.80
Cheers,
Brent
Re: A group of ten candy bars has an average cost of $0.89 per c
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24 Mar 2019, 10:02
24 Mar 2019, 10:02
Expert Reply
I agree.
Regards
Regards
