英语翻译

题目

英语翻译
A salad bar has ingredients,excluding the dressing.How many different salads are possible where two salads are different if they don't include indentical ingredients?You can either include or exclude each of the seven ingredients in your salad,which means there are 2 choices for each ingredient.According to the multiplication rule,there are 2*7=128 ways of making these yes-no choices.原问题哪里来的include和exclude东西?
原题打错了A salad bar has 7 ingredients,excluding the dressing.How many different salads are possible where two salads are different if they don't include indentical ingredients?

答案

有7种原料可选（黄瓜、西红柿、洋葱等）,一共有多少种方法做沙拉,使得任意两种沙拉都不相同（其实就是可以做出多少种不同的沙拉）?
答案是告诉你,每种原料都有放和不放两种选择（yes/no）,所以一共有2的7次方种不同的选择.你知道,我不是学数学的,我有点忘了排列组合知识,但是拿3和4做实验,的确都是2的3次方和4次方.
【不过我觉得从实际出发,答案应该是127,因为什么原料都不放、只放调料的就不是沙拉了.】