题目内容
能用简便方法计算就用简便方法计算
①6.9×3.6-4.84÷0.4 | ②4.75+8.4÷(9.2-6.8) |
③1.2÷[2.5(4.3-2.7)] | ④4.5×(0.75-0.356)+9.23 |
⑤0.88÷0.8+3.2×1.25 | ⑥5.4+(0.63+0.555÷1.5) |
解:①6.9×3.6-4.84÷0.4,
=24.84-12.1,
=12.74;
②4.75+8.4÷(9.2-6.8),
=4.75+8.4÷2.4,
=4.75+3.5,
=8.25;
③1.2÷[2.5×(4.3-2.7)],
=1.2÷[2.5×1.6],
=1.2÷4,
=0.3;
④4.5×(0.75-0.356)+9.23,
=4.5×0.394+9.23,
=1.773+9.23,
=11.003;
⑤0.88÷0.8+3.2×1.25,
=1.1+4×0.8×1.25,
=1.1+4×(0.8×1.25),
=1.1+4×1,
=1.1+4,
=5.1;
⑥5.4+(0.63+0.555÷1.5),
=5.4+(0.63+0.37),
=5.4+1,
=6.4.
分析:①先算乘除,再算减法;
②先算括号内的,再算括号外的除法,最后算括号外的加法;
③先算小括号内的,再算中括号内的,最后算括号外的;
④先算括号内的,再算括号外的乘法,最后算括号外的加法;
⑤先算乘除,再算加法,在计算3.2×1.25是,把3.2看作4×0.8,运用乘法结合律简算;
⑥先算括号内的除法,再算括号内的加法,最后算括号外的.
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律简便计算.
=24.84-12.1,
=12.74;
②4.75+8.4÷(9.2-6.8),
=4.75+8.4÷2.4,
=4.75+3.5,
=8.25;
③1.2÷[2.5×(4.3-2.7)],
=1.2÷[2.5×1.6],
=1.2÷4,
=0.3;
④4.5×(0.75-0.356)+9.23,
=4.5×0.394+9.23,
=1.773+9.23,
=11.003;
⑤0.88÷0.8+3.2×1.25,
=1.1+4×0.8×1.25,
=1.1+4×(0.8×1.25),
=1.1+4×1,
=1.1+4,
=5.1;
⑥5.4+(0.63+0.555÷1.5),
=5.4+(0.63+0.37),
=5.4+1,
=6.4.
分析:①先算乘除,再算减法;
②先算括号内的,再算括号外的除法,最后算括号外的加法;
③先算小括号内的,再算中括号内的,最后算括号外的;
④先算括号内的,再算括号外的乘法,最后算括号外的加法;
⑤先算乘除,再算加法,在计算3.2×1.25是,把3.2看作4×0.8,运用乘法结合律简算;
⑥先算括号内的除法,再算括号内的加法,最后算括号外的.
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律简便计算.
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