Question

这道题可以简便计算吗？

Answer 1

可桥局铅以简便敏好计算
1.9x2.5+8.1x7.5
=1.9x2.5+8.1x(2.5+5)
=1.9x2.5+8.1x2.5+8.1x5
=（1.9+8.1）腊困x2.5+40.5
=10x2.5+40.5
=25+40.5
=65.5

追问

两个8．1哪来的

追答

乘法分配律

8.1x（2.5+5）=8.1x2.5+8.1x5

追问

哦

Answer 2

1.9x2.5+8.1x7.5
=1.9x2.5+8.1x(2.5+5)
=1.9x2.5+8.1x2.5+8.1x5
=（1.9+8.1）x2.5+（早衫8+0.1）脊睁宽樱亮×5
=10x2.5+8×5+0.1×5
=25+40+0.5
=65.5

Answer 3

399+(154+201) =399+201+154 =600+154 =754 480+325+75 =480+(325+75) =480+400 =880 78+53+47+22 = (78+22)+(53+47) =100+100 =200 91+89+11 =90+(89+11) =90+100 =190 36+18+64 = (36+64)+18 =100+18 =118 168+250+32 = (168+32)+250 =200+250 =450 85+41+15+59 =(85+15)+(41+59) =100+100 =200