问题补充:
递等式计算.(能巧算的要巧算)
3×80+320?????????
500-6×70
246+118+82+54????
49×6-39×6.
答案:
解:(1)3×80+320,
=240+320,
=560;
(2)500-6×70,
=500-420,
=80;
(3)246+118+82+54,
=(246+54)+(118+82),
=300+200,
=500;
(4)49×6-39×6,
=(49-39)×6,
=10×6,
=60.
解析分析:(1)先算乘法,再算加法;
(2)先算乘法,再算加法;
(3)运用加法交换律、结合律进行简算;
(4)运用乘法分配律进行简算.
点评:此题考查了整数四则混合运算的顺序,能简算的要进行简算.