《2025年快乐口算五年级数学上册人教版》

1 口算。
$4.2 + 3.6 = $
$9.1 - 7.8 = $
$60×0.3 = $
$4.1 + 9 = $
$18×0.1 = $
$5÷0.1 = $
$5.6÷0.7 = $
$0.85 - 0.7 = $
$6×4.3 = $
$0.42÷0.6 = $
$0.29 + 0.5 = $
$8.7÷0.3 = $
$0.25×0.4 = $
$12÷1.2 = $
$63.8×0 = $

答案： 1. $4.2 + 3.6 = 7.8$
2. $9.1 - 7.8 = 1.3$
3. $60×0.3 = 18$
4. $4.1 + 9 = 13.1$
5. $18×0.1 = 1.8$
6. $5÷0.1 = 50$
7. $5.6÷0.7 = 8$
8. $0.85 - 0.7 = 0.15$
9. $6×4.3 = 25.8$
10. $0.42÷0.6 = 0.7$
11. $0.29 + 0.5 = 0.79$
12. $8.7÷0.3 = 29$
13. $0.25×0.4 = 0.1$
14. $12÷1.2 = 10$
15. $63.8×0 = 0$

1. 当$a = 15$时,写出下面各式的结果。
$2a = $ $4a = $
$0.5a = $ $10a = $
$12.3 + a = $ $a - 5 = $
$a + 78 = $ $123 - a = $
$20a = $ $56 - a = $
$a÷5 = $ $95 + a = $
$a - 6.3 = $ $0.4a = $
$a + 78.5 = $ $100 - a = $
$80a = $ $150÷a = $

答案： $2a = 30$； $4a = 60$；
$0.5a = 7.5$； $10a = 150$；
$12.3 + a = 27.3$； $a - 5 = 10$；
$a + 78 = 93$； $123 - a = 108$；
$20a = 300$； $56 - a = 41$；
$a÷5 = 3$； $95 + a = 110$；
$a - 6.3 = 8.7$； $0.4a = 6$；
$a + 78.5 = 93.5$； $100 - a = 85$；
$80a = 1200$； $150÷ a = 10$。

2. 省略乘号写出下面各式。
$1×m = $ $x×4 = $
$3×b = $ $a×6 = $
$0.9×a = $ $n×5 = $
$x×7.6 = $ $n×n = $
$2.4×d = $ $x×88 = $

答案： $m$，$4x$，$3b$，$6a$，$0.9a$，$5n$，$7.6x$，$n^2$，$2.4d$，$88x$

3. 小明一家自驾轿车去旅游,每小时行驶$100km$,$x$小时行驶了多少千米？
小窍门 省略乘号时,一般把数字写在字母前面。

答案： $100x$