(2013•东城区模拟)计算下面各题,能简便计算的要简便计算

1个回答

  • 解题思路:(1)先去掉括号,再计算;

    (2)运用乘法分配律简算;

    (3)运用乘法结合律简算;

    (4)把分子和分母都运用乘法分配律简算,然后再化简;

    (5)1-[1/2×2]=1-[1/4]=[3/4]=[1/2]×[3/2];

    1-[1/3×3]=1-[1/9]=[8/9]=[2/3]×[4/3];

    由此化简求解.

    (1)7[4/15]-(2[4/15]-2.3),

    =7[4/15]-2[4/15]+2.3,

    =5+2.3,

    =7.3;

    (2)4.85×3[3/5]-3.6+6.15×3[3/5],

    =4.85×3.6-3.6+6.15×3.6,

    =(4.85-1+6.15)×3.6,

    =10×3.6,

    =36;

    (3)0.025×999×2.8×40÷2[4/5],

    =(0.025×40)×(2.8÷2.8)×999,

    =1×1×999,

    =999;

    (4)[2001×2001+2001/2002×2002−2002],

    =

    2001×(2001+1)

    2002×(2002−1),

    =[2001×2002/2002×2001],

    =1;

    (5)(1-[1/2×2])(1-[1/3×3])(1-[1/4×4])…(1-[1/2001×2001]),

    =([1/2]×[3/2])×([2/3]×[4/3])×([3/4]×[5/4])×…([2000/2001]×[2002/2001]),

    ═[1/2]×([3/2]×[2/3])×([4/3]×[3/4])×…([2001/2000]×

    点评:

    本题考点: 分数的四则混合运算;运算定律与简便运算;分数的简便计算;小数四则混合运算;分数的巧算.

    考点点评: 此题考查四则混合运算,要仔细观察算式的特点,灵活运用一些定律进行简便计算;较复杂的计算要先找出规律,然后根据规律化简求解.