用递等式计算(能简算的要简算) 20.9+10.2÷(5.2-3.5) 9.4×[1.28-(1.54-0.31)] 1

1个回答

  • 解题思路:(1)先算括号内的,再算括号外的除法,最后算加法.

    (2)先算小括号内的,再算中括号内的,最后算括号外的.

    (3)先算乘法,然后从左往右依次计算.

    (4)运用减法的性质简算.

    (5)先算括号内的,再算乘法,最后算加法.

    (6)先算小括号内的,再算中括号内的除法,然后算中括号内的减法,最后算括号外的乘法.

    (1)20.9+10.2÷(5.2-3.5)

    =20.9+10.2÷1.7

    =20.9+6

    =26.9

    (2)9.4×[1.28-(1.54-0.31)]

    =9.4×[1.28-1.23]

    =9.4×0.05

    =0.47

    (3)10.64+7.65×2.4+11.76

    =10.64+18.36+11.76

    =(10.64+18.36)+11.76

    =29+11.76

    =40.76

    (4)15.52-4.3-5.7

    =15.52-(4.3+5.7)

    =15.52-10

    =5.52

    (5)9.83×(3.8-2.3)+1.5×6.17

    =9.83×1.5+9.255

    =14.745+9.255

    =24

    (6)[(6.1-4.6)÷0.8-1]×0.4

    =[1.5÷0.8-1]×0.4

    =[1.875-1]×0.4

    =0.875×0.4

    =0.35

    点评:

    本题考点: 小数四则混合运算.

    考点点评: 此题考查了小数的四则混合运算,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.