1. 口算。
$3.6×0.3= $ $1.2×0.7= $ $16.5×4= $
$0.52×0.5= $ $2.3×60= $ $12.5×0.8= $
$4.8+5.2= $ $21.3×0.6= $ $60-5.31= $
$0.15×0.6= $ $30.1-7.8= $ $18.5×0.6= $
$3.6×0.3= $ $1.2×0.7= $ $16.5×4= $
$0.52×0.5= $ $2.3×60= $ $12.5×0.8= $
$4.8+5.2= $ $21.3×0.6= $ $60-5.31= $
$0.15×0.6= $ $30.1-7.8= $ $18.5×0.6= $
答案:
9
2. 在$◯$里填上“$>$”“$<$”或“$=$”。
$85×0.7◯ 85$ $38.2×0.1◯ 3.82×10$
$6.3×2.1◯ 6.3$ $5.4×0◯ 5.4$
$5.39×7◯ 7×5.39$ $2.5×0.32◯ 0.25×3.2$
$85×0.7◯ 85$ $38.2×0.1◯ 3.82×10$
$6.3×2.1◯ 6.3$ $5.4×0◯ 5.4$
$5.39×7◯ 7×5.39$ $2.5×0.32◯ 0.25×3.2$
答案:
$85×0.7<85$;
$38.2×0.1=3.82$,$3.82×10=38.2$,所以$38.2×0.1<3.82×10$;
$6.3×2.1>6.3$;
$5.4×0=0<5.4$;
$5.39×7=7×5.39$;
$2.5×0.32=0.8$,$0.25×3.2=0.8$,所以$2.5×0.32=0.25×3.2$。
答案依次为:<;<;>;<;=;=
$38.2×0.1=3.82$,$3.82×10=38.2$,所以$38.2×0.1<3.82×10$;
$6.3×2.1>6.3$;
$5.4×0=0<5.4$;
$5.39×7=7×5.39$;
$2.5×0.32=0.8$,$0.25×3.2=0.8$,所以$2.5×0.32=0.25×3.2$。
答案依次为:<;<;>;<;=;=
3. 列竖式计算,带$※$的题要验算。
$※4.8×3.6$ $0.028×0.65$
验算: (得数保留两位小数)
$※4.8×3.6$ $0.028×0.65$
验算: (得数保留两位小数)
答案:
```
4.8×3.6=17.28
4.8
×3.6
----
288
144
----
17.28
验算:
3.6
×4.8
----
288
144
----
17.28
0.028×0.65≈0.02
0.028
×0.65
------
140
168
------
0.01820
```
4.8×3.6=17.28
4.8
×3.6
----
288
144
----
17.28
验算:
3.6
×4.8
----
288
144
----
17.28
0.028×0.65≈0.02
0.028
×0.65
------
140
168
------
0.01820
```
4. 计算下面各题,怎样简便就怎样计算。
$0.25×0.9×0.4$ $5.4×6.3+6.3×4.6$
$3.17×101-3.17$ $1.25×8.8$
$0.25×0.9×0.4$ $5.4×6.3+6.3×4.6$
$3.17×101-3.17$ $1.25×8.8$
答案:
1. $0.25×0.9×0.4$
$=0.25×0.4×0.9$
$=0.1×0.9$
$=0.09$
2. $5.4×6.3+6.3×4.6$
$=(5.4 + 4.6)×6.3$
$=10×6.3$
$=63$
3. $3.17×101 - 3.17$
$=3.17×(101 - 1)$
$=3.17×100$
$=317$
4. $1.25×8.8$
$=1.25×(8+0.8)$
$=1.25×8+1.25×0.8$
$=10 + 1$
$=11$
$=0.25×0.4×0.9$
$=0.1×0.9$
$=0.09$
2. $5.4×6.3+6.3×4.6$
$=(5.4 + 4.6)×6.3$
$=10×6.3$
$=63$
3. $3.17×101 - 3.17$
$=3.17×(101 - 1)$
$=3.17×100$
$=317$
4. $1.25×8.8$
$=1.25×(8+0.8)$
$=1.25×8+1.25×0.8$
$=10 + 1$
$=11$
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