\(\dfrac{2727}{3131}=\dfrac{27.101}{31.101}=\dfrac{27}{31}\)

⇒\(\dfrac{27}{31}=\dfrac{2727}{3131}\)

\(\dfrac{27}{31}=\dfrac{27\times101}{31\times101}=\dfrac{2727}{3131}\)

\(\frac{27}{31}=\frac{27x10101}{31x10101}=\frac{272727}{313131}\)

27/31 = 272727/313131

`#3107.101107`

`a)`

Ta có:

\(\dfrac{2727}{3131}=\dfrac{2727\div27}{3131\div31}=\dfrac{27}{31}\)

Vì \(\dfrac{27}{31}=\dfrac{27}{31}\)

\(\Rightarrow\dfrac{27}{31}=\dfrac{2727}{3131}\)

`b)`

Ta có:

\(\dfrac{11}{31}=1-\dfrac{20}{31}=1-\dfrac{200}{310}\)

\(\dfrac{111}{311}=1-\dfrac{200}{311}\)

Vì \(\dfrac{200}{310}>\dfrac{200}{311}\)

\(\Rightarrow1-\dfrac{200}{310}< 1-\dfrac{200}{311}\)

\(\Rightarrow\dfrac{11}{31}< \dfrac{111}{311}.\)

27/31 = 2727/3131

11/31 bé hơn 111/311

27/31<2727/3131

11/31<111/311

\(a,\dfrac{2727}{3131}=\dfrac{2727:101}{3131:101}=\dfrac{27}{31}\\ Vậy:\dfrac{27}{31}=\dfrac{2727}{3131}\)

27 x \(\left(\frac{171717}{272727}+\frac{373737}{363636}\right)\)

= 27 x \(\left(\frac{17}{27}+\frac{37}{36}\right)\)

= 27 x \(\frac{17}{27}\)+  27 x \(\frac{37}{36}\)

= 17 + 27,75

= 44,75

\(\frac{178}{4}\)bạn nhé

a) \(\frac{1212}{1515}\):\(\frac{2727}{2525}\)

=   \(\frac{1212}{1515}\)* \(\frac{2525}{2727}\)

=     \(\frac{101.12}{101.15}\)* \(\frac{101.25}{101.27}\)

=      \(\frac{12}{15}\). \(\frac{25}{27}\)

=       \(\frac{20}{27}\)

b) ban co the viet ro hon de bai dc ko?

Bài làm

Ta đặt M=1/3+1/7+1/13+1/21+1/31+1/43+1/57+1/73+1/91
Vậy M<1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90 
       M< 1/2+1/2x3+1/3x4+1/4x5+1/5x6+1/6x7+1/7x8+1/8x9+1/9x10
      M< (1-1/2) +(1/2-1/3) +(1/3-1/4) +(1/4-1/5) +(1/5-1/6) +(1/6-1/7) +(1/7-1/8) +(1/8-1/9) +(1/9-1/10)
     M< 1-1/10 < 9/10      (1)
     Vì 9/10 < 1    (2)
     Từ(1) và (2) ta có : 1/3+1/7+1/13+1/21+1/31+1/43+1/57+1/73+1/91<1