Question 1209199
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An electronics store offers separate discount coupons of 5%, 10%, and 15%.
Bill uses one of each coupon to buy a computer with sticker price $1000.
When Bill gets his receipt, a dark smudge covers up the sales tax percentage, 
but he can see the final total at the very bottom of the receipt is $773.99
(a) What is the sales tax percentage? Round to the nearest tenth of a percent.
(b) If there wasn't any sales tax, how much would Bill spend? Round to the nearest penny.
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If I understand correctly, Bill uses 3 coupons of 5%, 10%, and 15%.


If so, then his buying price before the tax is

    (1-0.05)*(1-0.1)*(1-0.15)*1000 = 0.95*0.9*0.85*1000 = 726.75 dollars (the precise value).


Hence, the tax is  773.99 - 726.75 = 47.24 dollars.


It means that the tax rate is  {{{47.24/726.75}}} = 0.065002, or 6.5002%.


Round it as requested to get the answer to (a) as 6.5%.


The answer to (b) is  $726.75, which we got above.
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Solved.