用你喜欢的计算.
(1)2.5×1.25×32????????????????????
(2)206+178-239
(3)195×9+252????? ?
(4)2÷[-(+)].
网友回答
解:(1)2.5×1.25×32,
=2.5×1.25×8×4,
=2.5×4×(1.25×8),
=10×10,
=100;
(2)206+178-239,
=200+6+200-22-200-39,
=(200+200-200)-(22+39-6),
=200-55,
=145;
(3)195×9+252,
=(200-5)×9+200+52,
=200×9-5×9+200+52,
=1800-45+200+52,
=1800+200+(52-45),
=2000+7,
=2007;
(4)2÷[-(+)],
=2÷[-(+)],
=2÷[-],
=2÷[-],
=2÷,
=2×6,
=12.
解析分析:(1)把32看作8×4,运用乘法交换律和结合律简算;(2)把206看作200+6,178看作200-22,239看作200+39,运用加法交换律和结合律简算;(3)把195看作200-5,252看作200+52,运用加法交换律和结合律计算;(4)按运算顺序计算,先算先算括号内的加法,再算中括号内的减法,最后算括号外的除法.
点评:完成本题要注意分析式中数据,运用合适的简便方法计算.