Toán Lớp 6: 1/2.5+1/5.8+1/8.11+…+1/47.50

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1. 1/(2.5) + 1/(5.8) + 1/(8.11) + … + 1/(47.50)

   = 1/3 . 3 . (1/(2.5) + 1/(5.8) + 1/(8.11) + … + 1/(47.50))

   = 1/3 . (3/(2.5) + 3/(5.8) + 3/(8.11) + … + 3/(47.50))

   = 1/3 . (1/2 – 1/5 + 1/5 – 1/8 + … + 1/47 – 1/50)

   = 1/3 . (1/2 – 1/50)

   = 1/3 . 24/50

   = 4/25

    

   Trả lời
2. 1/2.5+1/5.8+1/8.11+…+1/47.50

   =1/3(3/2.5+3/5.8+3/8.11+…+3/47.50)

   =1/3(1/2-1/5+1/5-1/8+1/8-1/11+…+1/47-1/50)

   =1/3(1/2-1/50)

   =1/3(25/50-1/50)

   =1/3. 12/25

   =4/25

    

   Trả lời