Question

2/7÷2/3＝2/7×3/2( )

Answer 1

2/7÷2/3＝2/7×3/2( )

对

①3/4×7/8÷0.75 ②（2/5-3/8)×40 ③2/7-9/16×2/7

①3/4×7/8÷0.75
=(3\4÷0.75 )x7\8
=(3\4÷3\4)x7\8
=7\8
②（2/5-3/8)×40
=2\5x40-3\8x40
=16-15
=1
③2/7-9/16×2/7
=2\7x(1-9\16)
=2\7x7\16
=1\8

2/6x:2/3=3/5:4:7

解2/6x:2/3=3/5:4:7
应该是2/6x:2/3=3/5:4/7
即2/6x*4/7=2/3*3/5
即4/21x=3/5
即x=3/5*21/4=63/20

2/3{3/2【(2/5x-1)-3】-6}-7=1

2/3{3/2【(2/5x-1)-3】-6}-7=1
2/3{3/2【(2/5x-1)-3】-6}=8
3/2【(2/5x-1)-3】-6=12
(2/5x-1)-3=12
2/5x-1=15
2/5x=16
x=40

2/3×（3/2-3/7)

2/3×（3/2-3/7)
=2/3x3/2-2/3x3/7
=1-2/7
=5/7
，
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解比例 100:X=2/5:3/10 2/3:3/7=7/15:X

100:X=2/5:3/10
X=（100×3/10）÷2/5
X=75

2/3:3/7=7/15:X
X=（3/7×7/15）÷2/3
X=3/10

2/(3+7)+2/(7+11)+2/(11+15)+。。。+2/(43+47)=?

3+7类似的换成2*n+1+2*2n-1.....以此类推..结果就好算了

S=2/(1×3)+2^2/(3×5)+2^3/(5×7)+…+2^49/(97×99)，T=1/3+2/5+2^2/7+…+2^48/99,求S-T。

算不出来

-15×2/7-0.68×3/5+5/7×(-15)-2/5×0.68

-15×2/7-0.68×3/5+5/7×(-15)-2/5×0.68
=-15×（2/7+5/7）-0.68×（3/5+2/5）
=-15-0.68
=-15.68

(12/7×2/24+3/2)×3/2=

(12/7×2/24+3/2)×3/2

=(4/7+3/2)×3/2

=6/7+9/4

=87/28。