Toán Lớp 6: (1/20+1/30+1/42+1/56+1/72+1/90)xX-101010/202020

TRẢ LỜI

1. (1/20 + 1/30 + 1/42 + 1/56 + 1/72 + 1/90) x = 101010/202020

   => ( 1/4.5 + 1/5.6 + 1/6.7 + 1/7.8 + 1/8.9 + 1/9.10) x = (10.10101)/(20 . 10101)

   => ( 1/4 – 1/5 + 1/5 – 1/6 +….+ 1/9 – 1/10) x = 1/2

   => (1/4 – 1/10) x = 1/2

   => (  10/40 – 4/40) x= 1/2

   => 3/20 x = 1/2

   => x= 1/2 : 3/20

   => x= 1/2 . 20/3

   => x= 10/3

   Vậy x= 10/3

    

   Trả lời
2. Giải đáp: x = 10/3

   Lời giải và giải thích chi tiết:

   (1/20+1/30+1/42+1/56+1/72+1/90)x = 101010/202020

   ⇔(1/4 × 1/5 + 1/5× 1/6 + 1/6 × 1/7 + 1/7 × 1/8 + 1/8 × 1/9 + 1/9 × 1/10)x =  1/2

   ⇔(1/4 – 1/5 + 1/5 – 1/6 + 1/6 – 1/7 + 1/7 – 1/8 + 1/8 – 1/9 + 1/9 – 1/10)x =  1/2

     ⇔(1/4 – 1/10)x =  1/2

   ⇔3/20 × x = 1/2

   ⇔x = 1/2 ÷ 3/20

   ⇒ x = 10/3

   Trả lời