SAT备考 - 每日一题（36）买衣服打折

今天的数学题目是我们每次买衣服都会遇到的场景。关于买牛仔裤打折。 A pair of jeans that regularly costs $40 is on sale for 30% off. As part of a promotion, each customer will also receive an additional discount on the marked sale price at the cash register. If the final price of the jeans was $22.40, what additional discount was applied to the marked sale price? 一条原价40美元的牛仔裤正在打折，享受7折优惠。作为促销的一部分，每位顾客在收银台还会另外获得额外的折扣。如果牛仔裤的最终价格是22.40美元，那么,这个额外的折扣是多少？