Question

16．能简算的要简算
$\frac{13}{49}$×21+28×$\frac{13}{49}$；               （$\frac{3}{4}$+$\frac{5}{8}$）×32；             72×$\frac{5}{71}$．

Answer 1

分析 利用乘法分配律进行计算．

解答 解：（1）$\frac{13}{49}$×21+28×$\frac{13}{49}$
=$\frac{13}{49}$×（21+28）
=$\frac{13}{49}$×49
=13

（2）（$\frac{3}{4}$+$\frac{5}{8}$）×32
=$\frac{3}{4}$×$32+\frac{5}{8}$×32
=24+20
=44

（3）72×$\frac{5}{71}$
=（71+1）×$\frac{5}{71}$
=71×$\frac{5}{71}$+1×$\frac{5}{71}$
=5+$\frac{5}{71}$
=5$\frac{5}{71}$

点评 考查学生对乘法分配律的掌握情况．