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Thread: Basic Math Problem?

20130718, 23:22 #1
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Basic Math Problem?
An instrument store gives a 10% discount to all students off the original cost of an instrument. During a “Back to school” sale, an additional 15% is taken off the discounted price. Julie, a student at the local high school, purchases a flute for $306. How much did it originally cost?
Good luck,
Maud

20130719, 10:04 #2
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$400
Do I have to show my work, teacher?

20130719, 10:48 #3
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Or if one figures in 5% sales tax, $381 give or take a few pennies, but there are also a couple potential trick elements in the mix, like if the instrument was not purchased there or what original cost might actually mean.
Last edited by F.U.N. downtown; 20130719 at 10:51.

20130719, 10:58 #4
Not figuring in any tax, the original price was $345.76.
Update  should be $353.76.Last edited by mrjimphelps; 20130719 at 11:10. Reason: recalculated

20130719, 11:01 #5

20130719, 11:11 #6
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It's easy maths: $306 / 0.9 / 0.85 = $400. But surely it would, in reality, be priced at $399.99?!
BATcher
Correlation is not causation.

20130719, 11:45 #7
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20130719, 12:41 #8

20130719, 13:22 #9
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Ya, and just divide by the sales tax amount prior to the two discounts for extra credit.
306/1.05/.85/.9=$380.95

20130720, 02:29 #10
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In the UK, although we have an iniquitous rate  20% usually  of "Value Added Tax" (VAT), it is always included in the price for consumer purchases, so "the price you see is the price you pay" (haggling excepted).
For electronic goods and software, there seems to be a special "$1 translates to £1" conversion rate, which is why the UK is often referred to by nonnative computer and software manufacturers as "Treasure Island". I have no idea whether this conversion rate also applies to the cost of flutes...BATcher
Correlation is not causation.

20130720, 12:07 #11
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This was an actual question given in a math class for education of immigrants to achieve a GED. The answer choices offered were:
A. $325.00
B. $375.00
C. $400.00
D. $408.00
E. $425.00
The most selected and also incorrect answer was $408.00 achieved by adding the 2 discounts (25%), calculating a discount of $102.00, then subtracting it from $408.00 which was a final price of $306.00.

20130720, 13:01 #12
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A 10% discount OFF the original price leaves 90% ON the original price.
If X is the original price, the first resulting price is 0.9X.
Then, if 15% is OFF this discounted price, that leaves 85% ON the price.
So, 0.85 x 0.9 x X = 306 (purchase).
Then, X = 306/0.765 = $400 as the original price.
Check it: $400 with a 10% discount = $360 ($40 off).
Then, 360 with a 15% discount = $54 off the $360.
So, 360  54 = $306.Last edited by kweaver; 20130720 at 13:19.

20130720, 16:08 #13
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When I was in London some years ago, the same seemed to apply to books, especially paperbacks. Whatever number the US publisher printed on the book, that was the number of pounds charged. The currency exchange rate at the time was about 1.75 to 1, plus the fee at the exchange kiosk.