Question

用简便计算。

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Answer 1

9.78×99+9.78 5.7×10.1
=5.7×(10+0.1)
=9.78×(99+1) =5.7×10+5.7×0.1
=9.78×100 =57+0.57
=978 =57.57

12.5×4.1×0.8 5.6×1.25
=12.5×0.8×4.1 =0.8×1.25×7
=10×4.1 =10×7
=41 =70

3.54×9.9+3.54+0.1
=3.54×(9.9+
0.1)+3.54+0.1-3.54×0.1
=3.54×10+3.64-0.354
=35.4+3.286
=38.686

(2.5-0.25）×4 0.8×1.2×12.5
=2.5×4-0.25×4 =0.8×12.5×1.2

=10-1 =10×1.2
=9 =12

15×10.2 43×9.9
=15×(10+8.2) =43×(10-0.1）
=15×10+15×0.2 = 43×10-43×0.1
=150+3 =430-4.3
=153 =425.7

0.59×(0.5×0.2)
=0.59×0.1
=0.059

Answer 2

9.78X99+9.78 5.7Ⅹ10.1
=9.78x(99+1) =5.7ⅹ10+5.7x0.1
=57+0.57
=57.57
=9.78ⅹ100
=978
12.5X4.1x0.8
=12.5X0.8X4.1
=10′ⅹ4.1
=41，

追问

不止这么多吧

我还是有几道题不会写

追答

简便计算用运算定律，多看例题，会背运算定律，找准规律＇，举一反三。