下面各题怎样简便就怎样计算(求未知数X).
5.02-1.37-2.63?????
×(+)+0.8??????
?:X=0.32:4.8??????
1.25×2.5×32??????????
11÷〔×(+)〕
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解:(1)5.02-1.37-2.63;
=5.02-(1.37+2.63),
=5.02-4,
=1.02;
(2?)×(+)+0.8,
=×+×+0.8,
=2+1.2+0.8,
=2+(1.2+0.8),
=2+2,
=4;
(3):x=0.32:4.8,
????0.32x=0.2×4.8,
????0.32x=0.96,
0.32x÷0.32=0.96÷0.32,
????????? x=3;
(4)1.25×2.5×32,
=(1.25×8?)×(2.5×4),
=10×10,
=100;
(5)11÷[×(+)],
=11÷[×],
=11÷;
=22.
解析分析:(1)利用一个数连续减去两个数,等于这个数减去这两个数的和计算:
(2)×(+)利用乘法分配律计算简便,然后利用加法结合律计算;
(3)比例的基本性质“两外项之积等于两内项之积”,把比例转化为0.32x=×4.8,利用等式的基本性质方程的两边同时除以0.32求解;
(4)把32拆成4×8,利用乘法结合律1.25×8,2.5×4,这样计算简便;
(5)按运算顺序直接计算即可.
点评:按照四则混合运算的运算顺序来解答,能简算的要间算.