AMC10 2005 A

AMC10 2005 A · Q5

AMC10 2005 A · Q5. It mainly tests Money / coins, Basic counting (rules of product/sum).

A store normally sells windows at $100 each. This week the store is offering one free window for each purchase of four. Dave needs seven windows and Doug needs eight windows. How many dollars will they save if they purchase the windows together rather than separately?

一家商店正常出售窗户每个 100 美元。本周商店提供每购买四个窗户赠送一个免费窗户。Dave 需要七个窗户，Doug 需要八个窗户。如果他们一起购买而不是单独购买，能节省多少美元？

(A) 100 100

(B) 200 200

(D) 400 400

(E) 500 500

Answer

Correct choice: (A)

正确答案：（A）

Solution

(A) If Dave buys seven windows separately he will purchase six and receive one free, for a cost of \$600. If Doug buys eight windows separately, he will purchase seven and receive one free, for a total cost of \$700. The total cost to Dave and Doug purchasing separately will be \$1300. If they purchase fifteen windows together, they will need to purchase only 12 windows, for a cost of \$1200, and will receive 3 free. This will result in a savings of \$100.

（A）如果戴夫单独购买七扇窗户，他将购买六扇并免费获得一扇，费用为 \$600。若道格单独购买八扇窗户，他将购买七扇并免费获得一扇，总费用为 \$700。戴夫和道格分别购买的总费用为 \$1300。如果他们一起购买十五扇窗户，他们只需购买 12 扇，费用为 \$1200，并将免费获得 3 扇。这将节省 \$100。

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