Taking into account the discount

Everyone just loves those buy-one-get-one-free coupons or the percentage off the total discounts. These promotions get you in the door and are good for everyone involved. Sometimes you have to pay tax on the amount before the discount, and sometimes you pay tax on the lesser amount. It depends on what the product is — and if the merchant knows how to figure it correctly. That s why you need to be aware of what s going on so you can check the computations. 

The Problem Your favorite restaurant is offering a free second entree, as long as it costs less than the entree you re paying for. This is how most of the buy-one-get-one-free promotions work. You ll pay tax on the reduced price, but you need to tip the waitress based on the total cost before the discount. Your entree costs 19.95, and your friend s entree costs 21.95. You ve ordered beverages totaling 16 and shared an appetizer that costs 6.95. The tax (sales plus restaurant tax) comes to 10.5 percent, and you want to give a 20 percent tip. You and your friend will split the bill. How much will each of you pay  

You re going to pay tax on all the items except the less-pricey meal, so add up all the items — food and beverages — except the 19.95 and compute the tax on that. You re going to figure the tip on all the items except the tax, so you ll need a different sum to do that computation. Last, you ll add up the cost of the items you re paying for, the tax, and the tip. Divide that total by 2, and you ll have the amount that each of you owes. 

Your total cost is the cost of the meals plus the tax plus the tip. Add 44.90 + 4.71 + 12.97 = 62.58. Divide that by 2, and each of you owes 31.29. Now, I know that in practice, most people would round the tip up to 13, but that doesn t really change the amount by much. 

Simple interest is the interest computed when compounding doesn t occur. The interest in a savings account compounds, because, if you don t withdraw any of the money you ve invested, your interest earns interest. With compound interest, the amount of interest earned is added to the account total, and then the new interest is figured on the new total. Simple interest is computed only on the beginning amount. 

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Taking into account the discounts offered by the suppliers e for raw material r for a set of discount intervals d, which are denoted by DFgrd, the total amount of money to be invested in raw materials is the following ... 

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