怎样简便就怎样计算28.4×99+28.43.6×20.10.25×16.7-0.25×0.712.5×(100+0.8

1个回答

  • 解题思路:(1)(2)(3)(4)(9)根据乘法分配律计算;

    (5)根据乘法交换律和结合律计算;

    (6)根据乘法结合律计算;

    (7)变形为(0.125×8)×(4×2.5)计算;

    (8)先变形为8×6.3-8×5.3,再根据乘法分配律计算.

    (1)28.4×99+28.4

    =28.4×(99+1)

    =28.4×100

    =2840

    (2)3.6×20.1

    =3.6×(20+0.1)

    =3.6×20+3.6×0.1

    =72+0.36

    =72.36

    (3)0.25×16.7-0.25×0.7

    =0.25×(16.7-0.7)

    =0.25×4×4

    =1×4

    =4

    (4)12.5×(100+0.8)

    =12.5×100+12.5×0.8

    =1250+10

    =1260

    (5)4×0.8×12.5×2.5

    =(4×2.5)×(0.8×12.5)

    =10×10

    =100

    (6)(4.2×2.5)×0.4

    =4.2×(2.5×0.4)

    =4.2×1

    =4.2

    (7)0.125×32×2.5

    =(0.125×8)×(4×2.5)

    =1×10

    =10

    (8)0.8×63-8×5.3

    =8×6.3-8×5.3

    =8×(6.3-5.3)

    =8×1

    =8

    (9)5.4×9.9

    =5.4×(10-0.1)

    =5.4×10-5.4×0.1

    =54-0.54

    =53.46

    点评:

    本题考点: 小数四则混合运算.

    考点点评: 考查了运算定律与简便运算,四则混合运算.注意运算顺序和运算法则,灵活运用所学的运算定律简便计算.