解题思路:(1)和(5)先通分再计算;
(2)连续减去两个数,等于减去这两个数的和进行简算即可
(3)和(6)根据加法交换律和结合律进行简算;
(4)把3.2拆成4×4×0.2,再根据乘法交换律和结合律进行简算.
(1)[7/8]+[3/4]-[11/12],
=[21/24]+[18/24]-[22/24],
=[21+18−22/24],
=[17/24];
(2)[15/11]-[3/8]-[5/8],
=[15/11]-([3/8]+[5/8]),
=[15/11]-1,
=[4/11];
(3)[5/9]+[7/12]+[4/9],
=([5/9]+[4/9])+[7/12],
=1+[7/12],
=1[7/12];
(4)25×0.25×3.2,
=25×0.25×(4×4×0.2),
=(25×4)×(0.25×4)×0.2,
=100×1×0.2,
=20;
(5)6-([3/4]-[2/5]),
=6-([15/20]-[8/20]),
=6-[7/20],
=5
13
点评:
本题考点: 分数的加法和减法;运算定律与简便运算;小数乘法.
考点点评: 分数的加减法,一般先通分再计算,能简算的要简算.