2026年口算基础训练四年级数学下册人教版第12页答案
2根据加法运算定律填空
490+ 320 = (
) + 490
250+ (
) = 30 + 250
35+ 48 = (
) + (
)
78+ (
) = 53 + (
)
(
) + 19 = (
) + 48
a + (
) = b + (
)
(
) + c = (
) + b
△ + (
) = ○ + (
)
(
) + ■ = (
) + ●
(
) + a = (
) + (
)
31+ (69 + 54) = (
+
) + 54
(35 + 48) + 152 = 35 + (
+
)
63+ (47 + 36) = (
+
) + 36
+ (105 + 162) = (95 +
) +
(
+
) + 84 = 37 + (116 +
)
★ + (
+ ■) = (
+ ●) +

(○ +
) + △ =
+ (◇ +
)

答案

1. $490 + 320 = \boxed{320} + 490$
2. $250 + \boxed{30} = 30 + 250$
3. $35 + 48 = \boxed{48} + \boxed{35}$
4. $78 + \boxed{53} = 53 + \boxed{78}$
5. $\boxed{48} + 19 = \boxed{19} + 48$
6. $a + \boxed{b} = b + \boxed{a}$
7. $\boxed{b} + c = \boxed{c} + b$
8. $△ + \boxed{○} = ○ + \boxed{△}$
9. $\boxed{●} + ■ = \boxed{■} + ●$
10. $\boxed{●} + a = ● + \boxed{a}$（或 $\boxed{a} + a = a + \boxed{a}$ 特殊情况需保证等式成立如a=●,合理即可）
11. $31 + (69 + 54) = (\boxed{31} + \boxed{69}) + 54$
12. $(35 + 48) + 152 = 35 + (\boxed{48} + \boxed{152})$
13. $63 + (47 + 36) = (\boxed{63} + \boxed{47}) + 36$
14. $\boxed{95} + (105 + 162) = (95 + \boxed{105}) + 162$
15. $(\boxed{37} + \boxed{116}) + 84 = 37 + (116 + \boxed{84})$
16. $★ + (\boxed{●} + ■) = (\boxed{★} + ■) + ●$（答案不唯一，合理组合如加法交换律保证等式成立即可）
17. $(○ + \boxed{◇}) + △ = ○ + (◇ + \boxed{△})$
计算
34+ (
) = 100
(
) + 13 = 100
118+ (
) = 200
29+ (
) = 100
246+ (
) = 300
48+ (
) = 200
129+ (
) = 200
57+ (
) = 300
(
) + 84 = 400
(
) + 68 = 900
143+ (
) = 700
(
) + 543 = 700
(
) + 666 = 900
196+ (
) = 900

493+ (
) = 600
(
) + 167 = 800
(
) + 167 = 1000
(
) + (
) = 1000

答案

1.
$100 - 34 = 66$；
2.
$100 - 13 = 87$；
3.
$200 - 118 = 82$；
4.
$100 - 29 = 71$；
5.
$300 - 246 = 54$；
6.
$200 - 48 = 152$；
7.
$200 - 129 = 71$；
8.
$300 - 57 = 243$；
9.
$400 - 84 = 316$；
10.
$900 - 68 = 832$；
11.
$700 - 143 = 557$；
12.
$700 - 543 = 157$；
13.
$900 - 666 = 234$；
14.
$900 - 196 = 704$；
15.
$600 - 493 = 107$；
16.
$800 - 167 = 633$；
17.
$1000 - 167 = 833$；
18.答案不唯一，如$500+500 = 1000$。