第三天卖完后余下:
12÷(1-
1
5 ),
=12÷
4
5 ,
=12×
5
4 ,
=15(袋);
第二天卖出后余下:
(15+12)÷(1-
1
4 ),
=27÷
3
4 ,
=27×
4
3 ,
=36(袋);
第一天卖出后余下:
(36+12)÷(1-
1
3 ),
=48÷
2
3 ,
=48×
3
2 ,
=72(袋);
总数为:
(72+12)÷(1-
1
2 ),
=84 ÷
1
2 ,
=84×2,
=168(袋);
答:这批大米共168袋.
第三天卖完后余下:
12÷(1-
1
5 ),
=12÷
4
5 ,
=12×
5
4 ,
=15(袋);
第二天卖出后余下:
(15+12)÷(1-
1
4 ),
=27÷
3
4 ,
=27×
4
3 ,
=36(袋);
第一天卖出后余下:
(36+12)÷(1-
1
3 ),
=48÷
2
3 ,
=48×
3
2 ,
=72(袋);
总数为:
(72+12)÷(1-
1
2 ),
=84 ÷
1
2 ,
=84×2,
=168(袋);
答:这批大米共168袋.