99×0.625+0.625=(99+1)×0.625=100×0.625=62.5
99×0.625+0.625=（99+1）×0.625=100×0.625=62.5
（100－1）x0.625＋0.625＝100x0.625－0.625＋0.625＝100x0.625＝62.5
（99十1）x0.625二62.5
