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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 7: 5/2.5 + 5/5.8 + … + 5/302.305

Toán Lớp 7: 5/2.5 + 5/5.8 + … + 5/302.305

Comments ( 2 )

  1. $\\$
    5/(2.5) + 5/(5.8) + … + 5/(302 . 305)
    = 5 . [1/(2.5)+1/(5.8)+…+1/(302 . 305)]
    = 5 . 1/3 . [1/2 – 1/5 + 1/5 – 1/8 + … + 1/302 – 1/305]
    = 5/3 . [1/2 + (-1/5 + 1/5)+…+(-1/302 +1/302)-1/305]
    = 5/3 . [1/2 – 1/305]
    = 5/3 . [305/610 – 2/610]
    = 5/3 . 303/610
    = 101/122
     

  2. Giải đáp:
    5/2.5 + 5/5.8 + … + 5/302.305=101/122
    Lời giải và giải thích chi tiết:
    5/2.5 + 5/5.8 + … + 5/302.305
    =5/3.(3/2.5+3/5.8+…+3/302.2305)
    =5/3.(1/2-1/5+1/5-1/8+…+1/302-1/305)
    =5/3.(1/2-1/305)
    =5/3.(305/610-2/610)
    =5/3. 303/610
    =101/122

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222-9+11+12:2*14+14 = ? ( )

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