Question

4.2+4.6+5+5.4+……+11+11.4这道题怎么做？

要巧算
1.25x5.6+2.50x4.4
6.25x0.16+3.7x0.84+25.5x0.084
1927x37+197.2x1.9-986x70.38
0.2+o.4+0.6+……+1.6+1.8+2
这3道题怎么做?要巧算

Answer 1

1式4.2+4.6+5+5.4+……+11+11.4
2式11.4+11+······+5.4+5+4.6+4.2
1式+2式=11.4+4.2+11+4.6+········+11.4+4.2
一式和二式各第一个数加起来=15.6，各第二个数加起来=15.6，······一共19项
=15.6*19=296.4
所以原式=296.4/2=188.2

1.25x5.6+2.50x4.4
=1.25*（5.6+8.8）=18

6.25x0.16+3.7x0.84+25.5x0.084
=0.16*（6.25+5.25*3.7+0.525*25.5）

=39.0625*0.16=6.25

0.2+o.4+0.6+……+1.6+1.8+2与第一个解法相同

Answer 2

等差数列求和公式：（首项+末项）*项数除以2，
1.25*8*0.7+2.5*4*0.4
第二题是提取公因式0.16
第三题提197.2
第四题还是等差数列求和
希望能帮到你，满意请采纳，谢谢

Answer 3

原式=（4.2+11.4）×[(11,4-4.2)÷o.4+1]/2=148.2
1.25x5.6+2.50x4.4
=1.25×8×0.7+2.5×4×1.1
=10×0.7+10×1.1
=18
6.25x0.16+3.7x0.84+25.5x0.084
=6.25×0.16+0.84×(3.7+2.55)
=6.25×0.16+6.25×0.84
=6.25×(0.16+0.84)
=6.25
1927x37+197.2x1.9-986x70.38
=1927×37+986×1.9÷5-986×70.38
=1972×37-986×70
=986×37×2-986×70
=986×(74-70)
=3944
0.2+o.4+0.6+……+1.6+1.8+2
=(0.2+2)×[(2-0.2)÷0.2+1]/2
=11

Answer 4

不是等差求和啊……高中基本公式就可以啊