一、口算。
$3.4×0.4=$
$4.5÷0.9=$
$12.5×0.2=$
$1.52÷0.08=$
$8.4÷0.4=$
$5×4=$
$\frac {2}{9}+\frac {4}{15}=$ $\frac {2}{3}+\frac {5}{14}=$ $\frac {4}{7}+\frac {4}{7}=$
$\frac {5}{7}-\frac {2}{5}=$ $\frac {5}{9}-\frac {1}{6}=$ $\frac {3}{4}-\frac {3}{10}=$
$3.4×0.4=$
1.36
$0.9+2.01=$2.91
$12.5×8=$100
$4.5÷0.9=$
5
$0.42÷7=$0.06
$5.5+0.25=$5.75
$12.5×0.2=$
2.5
$2.97÷10=$0.297
$4.8÷0.16=$30
$1.52÷0.08=$
19
$6.7+0.33=$7.03
$0.64÷0.4=$1.6
$8.4÷0.4=$
21
$12.6-0.9=$11.7
$2.6+3.8=$6.4
$5×4=$
20
$6.5×0.2=$1.3
$2-0.01=$1.99
$\frac {2}{9}+\frac {4}{15}=$ $\frac {2}{3}+\frac {5}{14}=$ $\frac {4}{7}+\frac {4}{7}=$
$\frac {5}{7}-\frac {2}{5}=$ $\frac {5}{9}-\frac {1}{6}=$ $\frac {3}{4}-\frac {3}{10}=$
答案
一、1.36 2.91 100
5 0.06 5.75
2.5 0.297 30
19 7.03 1.6
21 11.7 6.4
20 1.3 1.99
5 0.06 5.75
2.5 0.297 30
19 7.03 1.6
21 11.7 6.4
20 1.3 1.99
二、计算长方体和正方体的表面积。


答案
二、2.5×2.5×6=37.5(cm²)
(3.6×4.4+3.6×5.5+4.4×5.5)×2=119.68(cm²)
(3.6×4.4+3.6×5.5+4.4×5.5)×2=119.68(cm²)
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