题目内容
用简便方法计算. 7.26-2.38+12.74-7.62 |
67÷
|
| ||||||||||
87×
|
51×3.2+32×4.9. |
分析:(1)运用加法交换律和结合律以及减法的性质简算;
(2)运用除法的性质简算;
(3)运用乘法分配律的逆运算简算;
(4)把87看作88-1,运用乘法分配律简算;
(5)根据数字特点以及积不变的规律,把32×4.9改写成3.2×49,运用乘法分配律的逆运算简算.
(2)运用除法的性质简算;
(3)运用乘法分配律的逆运算简算;
(4)把87看作88-1,运用乘法分配律简算;
(5)根据数字特点以及积不变的规律,把32×4.9改写成3.2×49,运用乘法分配律的逆运算简算.
解答:解:(1)7.26-2.38+12.74-7.62,
=(7.26+12.74)-(2.38+7.62),
=20-10,
=10;
(2)67÷
÷12.5,
=67÷(
×12.5),
=67÷10,
=6.7;
(3)
×
+
×
,
=(
+
)×
,
=1×
,
=
;
(4)87×
,
=(88-1)×
,
=88×
-
,
=87-
,
=86
;
(5)51×3.2+32×4.9,
=51×3.2+3.2×49,
=(51+49)×3.2,
=100×3.2,
=320.
=(7.26+12.74)-(2.38+7.62),
=20-10,
=10;
(2)67÷
4 |
5 |
=67÷(
4 |
5 |
=67÷10,
=6.7;
(3)
7 |
13 |
9 |
17 |
9 |
17 |
6 |
13 |
=(
7 |
13 |
6 |
13 |
9 |
17 |
=1×
9 |
17 |
=
9 |
17 |
(4)87×
87 |
88 |
=(88-1)×
87 |
88 |
=88×
87 |
88 |
87 |
88 |
=87-
87 |
88 |
=86
1 |
88 |
(5)51×3.2+32×4.9,
=51×3.2+3.2×49,
=(51+49)×3.2,
=100×3.2,
=320.
点评:此题考查了学生运用运用性质和运算定律进行简便计算的能力.其中第(5)题也可这样计算:51×3.2+32×4.9=5.1×32+32×4.9=(5.1+4.9)×32=32×10=320.
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