题目内容
(2008?射洪县)计算下面各题,能简算的要用简便方法算.
①627+9105÷15
②5.78×99+5.78
③
×(
+0.25×
)
④78.5÷0.25÷4
⑤50
-45.75-4.25
⑥7.86+0.625×1.8÷4.5.
①627+9105÷15
②5.78×99+5.78
③
4 |
13 |
3 |
8 |
2 |
3 |
④78.5÷0.25÷4
⑤50
5 |
6 |
⑥7.86+0.625×1.8÷4.5.
分析:①先做9105÷15的商得607,再做627+607;
②利用分配律提取5.78,变成5.78×(99+1),再求5.78×100的积;
③先算括号里面的0.25×
得
,再算
+
的和的
,最后算
×
的积;
④一个数连续除以两个数等于这个数除以这两个数的积来计算,78.5÷0.25÷4=7.85÷(0.25×4),再算7.85÷1的商;
⑤一个数连续减去两个数等于这个数减去这两个数的和,50
-45.75-4.25=50
-(45.78+4.25),再算50
-50的差;
⑥先算0.625×1.8÷4.5的得数0.25,再算7.85+0.25的和.
②利用分配律提取5.78,变成5.78×(99+1),再求5.78×100的积;
③先算括号里面的0.25×
2 |
3 |
1 |
6 |
3 |
8 |
1 |
6 |
13 |
24 |
4 |
13 |
13 |
24 |
④一个数连续除以两个数等于这个数除以这两个数的积来计算,78.5÷0.25÷4=7.85÷(0.25×4),再算7.85÷1的商;
⑤一个数连续减去两个数等于这个数减去这两个数的和,50
5 |
6 |
5 |
6 |
5 |
6 |
⑥先算0.625×1.8÷4.5的得数0.25,再算7.85+0.25的和.
解答:解:①627+9105÷15,
=627+607,
=1234;
②5.78×99+5.78
=5.78×(99+1),
=5.78×100,
=578;
(3)
×(
+0.25×
),
=
×(
+
),
=
×
,
=
;
④78.5÷0.25÷4,
=7.85÷(0.25×4),
=7.85÷1,
=7.85;
⑤50
-45.75-4.25
=50
-(45.75+4.25),
=50
-50,
=
;
⑥7.86+0.625×1.8÷4.5,
=7.86+0.25,
=8.11.
=627+607,
=1234;
②5.78×99+5.78
=5.78×(99+1),
=5.78×100,
=578;
(3)
4 |
13 |
3 |
8 |
2 |
3 |
=
4 |
13 |
3 |
8 |
1 |
6 |
=
4 |
13 |
13 |
24 |
=
1 |
6 |
④78.5÷0.25÷4,
=7.85÷(0.25×4),
=7.85÷1,
=7.85;
⑤50
5 |
6 |
=50
5 |
6 |
=50
5 |
6 |
=
5 |
6 |
⑥7.86+0.625×1.8÷4.5,
=7.86+0.25,
=8.11.
点评:此题考查分数小数的四则运算,能简算的要简算.
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