1. 直接写得数。
$\frac{2}{3} × \frac{3}{4}=$
$\frac{7}{9} ÷ 7=$
$\frac{3}{4} × \frac{5}{6} × \frac{4}{15}=$
$\frac{7}{8} × 0=$
$\left(\frac{1}{2} - \frac{1}{3}\right) × 6=$
$\frac{2}{5} ÷ \frac{8}{15}=$
$\frac{1}{3} × \frac{2}{5}=$
$\frac{9}{20} ÷ \frac{9}{10}=$
$\frac{7}{12} × 12 × \frac{1}{23} × 23=$

$\frac{1}{2}$
$\frac{1}{9}$
$\frac{1}{6}$
0
1
$\frac{3}{4}$
$\frac{2}{15}$
$\frac{1}{2}$
7

2. 判断。(对的打“√”,错的打“×”。)
(1) $5 - \frac{3}{4} + \frac{1}{4}=5 - \left(\frac{3}{4} + \frac{1}{4}\right)=4$ ()
(2) $8 × \frac{3}{5} + 8 × \frac{2}{5} + 8=8 × \left(\frac{3}{5} + \frac{2}{5} + 8\right)=72$ ()
(3) $\left(3 + \frac{5}{6}\right) × 6=3 × 6 + \frac{5}{6} × 6=23$ ()

×
×
√

3. 计算。
$\frac{1}{5} + \frac{2}{7} ÷ \frac{3}{7}$
$\frac{1}{3} × \left(\frac{2}{3} - \frac{2}{5}\right) ÷ \frac{3}{5}$
$\left[1 - \left(\frac{1}{4} + \frac{1}{2}\right)\right] ÷ \frac{4}{5}$
$\frac{2}{7} × \left(1 ÷ \frac{3}{4} - \frac{3}{4} ÷ 1\right)$

$=\frac 15+\frac 23$
$ =\frac {13}{15}$
$=\frac 13×\frac 4{15}×\frac 53$
$ =\frac {4}{27}$
$=[1-\frac 34]÷\frac 45$
$ =\frac 14÷\frac 45$
$ =\frac 5{16}$
$=\frac 27×(\frac 43-\frac 34)$
$ =\frac 27×\frac 7{12}$
$ =\frac 16$