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

Toán Lớp 5: 5 + 5 + … + 5 = 5 x 8 8 x 11 233 x 236

Toán Lớp 5: 5 + 5 + … + 5 =
5 x 8 8 x 11 233 x 236

Comments ( 2 )

  1. Đặt:
    A = 5/(5xx8) + 5/(8xx11) + … + 5/(233xx236)
    3/5 xx A = 3/5 xx (5/(5xx8) + 5/(8xx11) + … + 5/(233xx236) )
    3/5 xx A = 3/(5xx8) + 3/(8xx11) + … + 3/(233xx236)
    3/5 xx A = 1/5 – 1/8 + 1/8 – 1/11 + … 1/233 – 1/236
    3/5 xx A = 1/5 – 1/236
    3/5 xx A = 231/1180
    A = 231/1180 : 3/5
    A = 77/236
     

  2. Lời giải và giải thích chi tiết:
    5/(5 xx 8) + 5/(8 xx 11) + ……. + 5/(233 xx 236)
    = 3/5 . (3/(5 xx 8) + 3/(8 xx 11) + ……. + 3/(233 xx 236))
    = 3/5 . (1/5 – 1/8 + 1/8 – 1/11 + ……. + 1/233 – 1/236)
    = 3/5 . (1/5 – 1/236)
    = 3/5 . 231/1180
    = 693/5900

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

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