(1)$2.4×0.5 = 0.5×2.4$,应用了(
乘法交换
)律。答案
乘法交换
(2)$(3.7×4)×2.5 = 3.7×(4×2.5)$,应用了(
乘法结合
)律。答案
乘法结合
(3)$2.5×(2 + 0.4) = 2.5×2 + 2.5×0.4$,应用了(
乘法分配
)律。答案
乘法分配
(4)$9.5×1.01=\Box×\Box+\Box×\Box$。
答案
9.5 1 9.5 0.01
(5)$14.5×2.8 - 2.8×4.5=\Box×(\Box◯\Box)$。
答案
2.8 14.5 - 4.5
(1)计算$3.6×0.25$最简便的算法是(
A.$3.6×0.2 + 3.6×0.05$
B.$3.6×0.5×0.5$
C.$0.25×4×0.9$
C
)。A.$3.6×0.2 + 3.6×0.05$
B.$3.6×0.5×0.5$
C.$0.25×4×0.9$
答案
C
(2)下列算式中,与$9.6×100.1$的结果不相等的是(
A.$9.6×100 + 9.6×0.1$
B.$(100 + 0.1)×9.6$
C.$9.6×10 + 9.6×0.1$
C
)。A.$9.6×100 + 9.6×0.1$
B.$(100 + 0.1)×9.6$
C.$9.6×10 + 9.6×0.1$
答案
C
解析
$9.6×100.1$
$=9.6×(100 + 0.1)$(与选项B相等)
$=9.6×100+9.6×0.1$(与选项A相等)
$=960 + 0.96$
$=960.96$
选项C:$9.6×10+9.6×0.1=96 + 0.96=96.96\neq960.96$
C
$=9.6×(100 + 0.1)$(与选项B相等)
$=9.6×100+9.6×0.1$(与选项A相等)
$=960 + 0.96$
$=960.96$
选项C:$9.6×10+9.6×0.1=96 + 0.96=96.96\neq960.96$
C
(3)$4.2×2.5 + 2.5×5.8$可以运用(
A.乘法分配律
B.乘法结合律
C.乘法交换律
A
)进行简便运算。A.乘法分配律
B.乘法结合律
C.乘法交换律
答案
A
3. 怎样简便就怎样算。
(1)$2.5×35.86×0.4$
(2)$2.5×3.2×1.25$
(3)$10.1×3.5$
(4)$9.18×0.3 + 9.18×9.7$
(1)$2.5×35.86×0.4$
(2)$2.5×3.2×1.25$
(3)$10.1×3.5$
(4)$9.18×0.3 + 9.18×9.7$
答案
(1) 2.5×35.86×0.4
=2.5×0.4×35.86
=35.86
(2) 2.5×3.2×1.25
=(2.5×4)×(0.8×1.25)
=10
(3) 10.1×3.5
=3.5×10+3.5×0.1
=35+0.35
=35.35
(4) 9.18×0.3+9.18×9.7
=9.18×(0.3+9.7)
=9.18×10
=91.8
=2.5×0.4×35.86
=35.86
(2) 2.5×3.2×1.25
=(2.5×4)×(0.8×1.25)
=10
(3) 10.1×3.5
=3.5×10+3.5×0.1
=35+0.35
=35.35
(4) 9.18×0.3+9.18×9.7
=9.18×(0.3+9.7)
=9.18×10
=91.8
4. 你能用简便方法计算下面各题吗?
(1)$3.58×67 + 35.8×3.7 - 0.358×40$
(2)$38.2×0.28 + 3.82×6.1 + 0.382×11$
(1)$3.58×67 + 35.8×3.7 - 0.358×40$
(2)$38.2×0.28 + 3.82×6.1 + 0.382×11$
答案
(1) 3.58×67 + 35.8×3.7 - 0.358×40
=3.58×(67+37-4)
=3.58×100
=358
(2) 38.2×0.28 + 3.82×6.1 + 0.382×11
=0.382×(28+61+11)
=0.382×100
=38.2
=3.58×(67+37-4)
=3.58×100
=358
(2) 38.2×0.28 + 3.82×6.1 + 0.382×11
=0.382×(28+61+11)
=0.382×100
=38.2
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