题目

Have you ever spent an afternoon in the backyard，maybe grilling or enjoying a basketball game, when suddenly you notice that everything goes quiet? There is an old phrase “calm before the storm,often used in a situation—a quiet period just before a great activity or. excitement. According to our own experience, we know there is actually calm before the storm. But what causes this calm? And is it always calm before the storm? Let's hear what scientists have to say..A period of calm happens in a particular kind of storm, the simplest kind of storm—a single-cell thunderstorm. In this type15．“白雪”洗衣机厂计划生产1500台洗衣机，前10天平均每天生产87台，剩下的要在一周内完成，这一周平均每天需生产洗衣机多少台？