簡便計算:23×4×8×25 要算式
原式=25X4X8X23
=100X8X23
=800X(20+3)
=800X20+800X3
=16000+2400
=18400
(25×39+25×61)×4,(75×99+75)×4能巧算嗎?如果能,怎麼巧算
(25×39+25×61)×4=[25x(39+61)]x4=(39+61)x(25x4)=10000
,(75×99+75)×4=[75x(99+1)]x4=(99+1)x75x4=30000
簡便計算39+61-39+61
39+61-39+61
39-39+(61+61)=122
37*15+21*45,怎樣算才簡便?
37*15+21*45
=37 x15 +21 x15 x3
=37x15+63x15
=(37+63)x15
=100x15
=1500