Question

13．簡便計算．
715-711+815-411              
7.15×99+0.715×10
99×$\frac{3}{98}$                          
0.625×0.2+$\frac{5}{8}$×$\frac{6}{5}$-62.5%×$\frac{2}{5}$．

Answer 1

分析 ①根據(jù)加法交換律及結(jié)合律計算；
②把0.715×10寫成7.15×1，再根據(jù)乘法分配律進(jìn)行計算；
③把99寫成98+1，再根據(jù)乘法分配律進(jìn)行計算；
④根據(jù)乘法分配律進(jìn)行計算．

解答 解：①715-711+815-411      
=（715-711）+（815-411）
=4+404
=408
        
②7.15×99+0.715×10
=7.15×99+7.15×1
=7.15×（99+1）
=7.15×100
=715

③99×$\frac{3}{98}$ 
=（98+1）×$\frac{3}{98}$
=98×$\frac{3}{98}$+1×$\frac{3}{98}$
=3+$\frac{3}{98}$
=3$\frac{3}{98}$
                        
④0.625×0.2+$\frac{5}{8}$×$\frac{6}{5}$-62.5%×$\frac{2}{5}$
=0.625×0.2+0.75-0.625×0.4
=0.75-（0.625×0.4-0.625×0.2）
=0.75-0.625×0.2
=0.75-0.125
=0.625

點評 完成本題要注意分析式中數(shù)據(jù)，運用合適的簡便方法計算．