(1)计算$1.7×\frac{1}{5}$时,可以把1.7化成分数($\quad$),然后计算($\quad$)$×$($\quad$)=($\quad$);也可以把$\frac{1}{5}$化成小数($\quad$),然后计算($\quad$)$×$($\quad$)=($\quad$)。
答案
$\frac{17}{10}$
$\frac{17}{10}$
$\frac{1}{5}$
$\frac{17}{50}$
$0.2$
$1.7$
$0.2$
$0.34$
$\frac{17}{10}$
$\frac{1}{5}$
$\frac{17}{50}$
$0.2$
$1.7$
$0.2$
$0.34$
(2)计算$\frac{5}{8}×2.4$时,因为8和2.4可以直接(),所以可以先()再相乘,结果是()。
答案
约分
约分
1.5
$\frac{5}{8}×2.4 = 5×0.3 = 1.5$
约分
1.5
$\frac{5}{8}×2.4 = 5×0.3 = 1.5$
(3)3.6m的$\frac{1}{6}$是()m;4.5t的$\frac{4}{5}$是()t。
答案
0.6;3.6
解析
$3.6×\frac{1}{6}=0.6$
$4.5×\frac{4}{5}=3.6$
$4.5×\frac{4}{5}=3.6$
(4)计算$\frac{5}{6}-\frac{3}{5}×\frac{2}{3}$时,应先算()法,再算()法。
答案
$\frac{5}{6}-\frac{3}{5}×\frac{2}{3}$
$=\frac{5}{6}-\frac{2}{5}$
$=\frac{13}{30}$
应先算(乘)法,再算(减)法。
$=\frac{5}{6}-\frac{2}{5}$
$=\frac{13}{30}$
应先算(乘)法,再算(减)法。
(5)根据运算律在$\boxed{□}$里填上适当的数。
$\frac{8}{9}×125×\frac{9}{8}=125×(\boxed{□}×\boxed{□})$
$\frac{4}{5}×13-\frac{4}{5}×3=\boxed{□}×(\boxed{□}-\boxed{□})$
$(\frac{1}{4}+\frac{4}{5})×20=\boxed{□}×\boxed{□}+\boxed{□}×\boxed{□}$
$\frac{8}{9}×125×\frac{9}{8}=125×(\boxed{□}×\boxed{□})$
$\frac{4}{5}×13-\frac{4}{5}×3=\boxed{□}×(\boxed{□}-\boxed{□})$
$(\frac{1}{4}+\frac{4}{5})×20=\boxed{□}×\boxed{□}+\boxed{□}×\boxed{□}$
答案
$\frac{8}{9}×125×\frac{9}{8}=125×(\boxed{\frac{8}{9}}×\boxed{\frac{9}{8}})$
$\frac{4}{5}×13-\frac{4}{5}×3=\boxed{\frac{4}{5}}×(\boxed{13}-\boxed{3})$
$(\frac{1}{4}+\frac{4}{5})×20=\boxed{\frac{1}{4}}×\boxed{20}+\boxed{\frac{4}{5}}×\boxed{20}$
$\frac{4}{5}×13-\frac{4}{5}×3=\boxed{\frac{4}{5}}×(\boxed{13}-\boxed{3})$
$(\frac{1}{4}+\frac{4}{5})×20=\boxed{\frac{1}{4}}×\boxed{20}+\boxed{\frac{4}{5}}×\boxed{20}$
2. 直接写出得数。
$1.2×\frac{3}{5}=$
$5.6×\frac{5}{7}=$
$\frac{7}{18}×0.36=$
$\frac{5}{24}×1.2=$
$\frac{5}{54}×0.6=$
$\frac{9}{16}×0.3=$
$\frac{12}{25}×2.5=$
$\frac{8}{45}×3.6=$
$1.2×\frac{3}{5}=$
$5.6×\frac{5}{7}=$
$\frac{7}{18}×0.36=$
$\frac{5}{24}×1.2=$
$\frac{5}{54}×0.6=$
$\frac{9}{16}×0.3=$
$\frac{12}{25}×2.5=$
$\frac{8}{45}×3.6=$
答案
$1.2×\frac{3}{5}=0.72$
$5.6×\frac{5}{7}=4$
$\frac{7}{18}×0.36=0.14$
$\frac{5}{24}×1.2=0.25$
$\frac{5}{54}×0.6=\frac{1}{18}$
$\frac{9}{16}×0.3=\frac{27}{160}$
$\frac{12}{25}×2.5=1.2$
$\frac{8}{45}×3.6=0.64$
$5.6×\frac{5}{7}=4$
$\frac{7}{18}×0.36=0.14$
$\frac{5}{24}×1.2=0.25$
$\frac{5}{54}×0.6=\frac{1}{18}$
$\frac{9}{16}×0.3=\frac{27}{160}$
$\frac{12}{25}×2.5=1.2$
$\frac{8}{45}×3.6=0.64$
3. 计算下面各题。
$\frac{2}{3}-\frac{3}{4}×\frac{8}{9}$
$\frac{1}{7}×\frac{7}{5}+1$
$\frac{1}{8}×(3-\frac{1}{4})$
$\frac{2}{5}×4×\frac{3}{4}$
$\frac{1}{2}×\frac{1}{15}+\frac{4}{15}×\frac{1}{2}$
$36×(\frac{5}{6}-\frac{4}{9})$
$63×\frac{2}{7}×\frac{5}{9}$
$(\frac{3}{8}+\frac{5}{6})×4.8$
$\frac{7}{10}×99+\frac{7}{10}$
$\frac{2}{3}-\frac{3}{4}×\frac{8}{9}$
$\frac{1}{7}×\frac{7}{5}+1$
$\frac{1}{8}×(3-\frac{1}{4})$
$\frac{2}{5}×4×\frac{3}{4}$
$\frac{1}{2}×\frac{1}{15}+\frac{4}{15}×\frac{1}{2}$
$36×(\frac{5}{6}-\frac{4}{9})$
$63×\frac{2}{7}×\frac{5}{9}$
$(\frac{3}{8}+\frac{5}{6})×4.8$
$\frac{7}{10}×99+\frac{7}{10}$
答案
3. (1)$48×\frac{5}{6}$
(2)$48×(1-\frac{1}{6})$
(3)$48×(1+\frac{1}{6})$
(2)$48×(1-\frac{1}{6})$
(3)$48×(1+\frac{1}{6})$
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