46+789+5425×2815×13×4
421-173-27720÷45420÷35÷2

解:(1)46+789+54,
=(46+54)+789,
=100+789,
=889;

(2)25×28,
=25×(4×7),
=25×4×7,
=100×7,
=700;

(3)15×13×4,
=15×4×13,
=60×13,
=780;

(4)421-173-27,
=421-(173+27),
=421-200,
=221;

(5)720÷45,
=(720÷9)÷(45÷9),
=80÷5,
=16;

(6)420÷35÷2,
=420÷(35×2),
=420÷70,
=6.
分析:(1)根據(jù)加法交換律簡算;
(2)先把28分解成4×7,再運(yùn)用乘法結(jié)合律簡算;
(3)根據(jù)乘法交換律簡算;
(4)根據(jù)減法的性質(zhì)簡算;
(5)根據(jù)除法商不變的規(guī)律簡算;
(6)根據(jù)除法的性質(zhì)簡算.
點(diǎn)評(píng):本題考查了四則混合運(yùn)算,注意運(yùn)算順序和運(yùn)算法則,靈活運(yùn)用所學(xué)的運(yùn)算定律進(jìn)行簡便計(jì)算.
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