分析:(1)先算括号内的乘法,再算括号内的减法,最后算括号外的除法;
(2)把分数化为小数,或者把小数化为分数,运用乘法分配律简算;
(3)运用乘法分配律简算;
(4)先算除法和乘法,再算减法;
(5)把101看作100+1,运用乘法分配律简算;
(6)先算括号内的乘法,再算括号内的减法,最后算括号外的除法.
(2)把分数化为小数,或者把小数化为分数,运用乘法分配律简算;
(3)运用乘法分配律简算;
(4)先算除法和乘法,再算减法;
(5)把101看作100+1,运用乘法分配律简算;
(6)先算括号内的乘法,再算括号内的减法,最后算括号外的除法.
解答:解:(1)
÷(5-3×
),
=
÷(5-2),
=
÷3,
=
×
,
=
;
(2)84×0.25+
×16,
=84×0.25+0.25×16,
=(84+16)×0.25,
=100×0.25,
=25;
(3)48×(
-
+
),
=48×
-48×
+48×
,
=16-24+12,
=4;
(4)
÷
-
×
,
=
×
-
×
,
=
-
,
=
;
(5)7.8×101,
=7.8×(100+1),
=780+7.8,
=787.8;
(6)(1-0.8×
)÷
,
=(1-0.6)÷
,
=0.4×
,
=0.5.
5 |
7 |
2 |
3 |
=
5 |
7 |
=
5 |
7 |
=
5 |
7 |
1 |
3 |
=
5 |
21 |
(2)84×0.25+
1 |
4 |
=84×0.25+0.25×16,
=(84+16)×0.25,
=100×0.25,
=25;
(3)48×(
1 |
3 |
1 |
2 |
1 |
4 |
=48×
1 |
3 |
1 |
2 |
1 |
4 |
=16-24+12,
=4;
(4)
1 |
2 |
2 |
5 |
2 |
3 |
7 |
10 |
=
1 |
2 |
5 |
2 |
2 |
3 |
7 |
10 |
=
5 |
4 |
7 |
15 |
=
47 |
60 |
(5)7.8×101,
=7.8×(100+1),
=780+7.8,
=787.8;
(6)(1-0.8×
3 |
4 |
4 |
5 |
=(1-0.6)÷
4 |
5 |
=0.4×
5 |
4 |
=0.5.
点评:考查了运算定律与简便运算,四则混合运算.注意运算顺序和运算法则,灵活运用所学的运算律简便计算.