怎样简便就怎样计算28.4×99+28.40.94×2.5-0.453.2×12.5×2.53.6×10.117.5÷0.25×17+138.7×9.9

Question

怎样简便就怎样计算

28.4×99+28.4	0.94×2.5-0.45	3.2×12.5×2.5
3.6×10.1	17.5÷0.25×17+13	8.7×9.9

Answer 1

（1）28.4×99+28.4
=28.4×（99+1）
=28.4×100
=2840；

（2）0.94×2.5-0.45
=2.35-0.45
=1.9；

（3）3.2×12.5×2.5
=0.4×8×12.5×2.5
=（0.4×2.5）×（8×12.5）
=1×100
=100；

（4）3.6×10.1
=3.6×（10+0.1）
=3.6×10+3.6×0.1
=36+0.36
=36.36；

（5）17.5÷0.25×17+13
=70×17+13
=1190+13
=1203；

（6）8.7×9.9
=8.7×（10-0.1）
=8.7×10-8.7×0.1
=87-0.87
=86.13．