《2025年口算训练六年级数学下册北师大版升级版》

初出茅庐
$x:6 = 2.5:2$ $x =$
$\frac{2}{3}:x = \frac{1}{3}:18$ $x =$
$\frac{1}{4}:4 = x:\frac{4}{5}$ $x =$
$\frac{1}{5}:\frac{3}{10} = 50:x$ $x =$
$x:\frac{1}{8} = \frac{1}{12}:\frac{1}{6}$ $x =$
$\frac{1.2}{8} = \frac{1.5}{x}$ $x =$

答案：

过关斩将
$\frac{2}{5}×0.25 =$
$2.5×0.4 =$
$1\frac{4}{5}×\frac{5}{9} =$
$5^{2}+3^{2} =$
$0.3 + 0.3^{2} =$
$4×87\%×2.5 =$
$\frac{1}{7}+\frac{1}{8}+\frac{6}{7} =$
$15 - 15×\frac{1}{5} =$
$\frac{9}{8}÷9×16 =$
$1 - \frac{4}{7}+\frac{3}{7} =$
$12.1 - 0.75 - \frac{1}{4} =$
$14÷(\frac{2}{5}+\frac{3}{10}) =$
$\frac{5}{8}÷5+\frac{3}{8} =$
$\frac{7}{6}-(\frac{1}{11}+\frac{1}{6}) =$
$\frac{3}{25}×75×\frac{8}{9} =$
$\frac{21}{33}÷\frac{8}{21}÷\frac{5}{8}×0 =$
$0×23÷18 =$
$9÷(1 - 0.99) =$

答案：

有一块$63$kg的铜锌合金，其中铜与锌的质量比是$3:4$，如果再加入$5$kg铜后，熔铸成新的合金，新的合金中铜和锌的质量比是多少？

答案：