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

Toán Lớp 5: N = `1/1 x 5` + `1/5 x 10` + `1/10 x 15` + `1/15 x 20` +-+ `1/2005 x 2010`

Toán Lớp 5: N = 1/1 x 5 + 1/5 x 10 + 1/10 x 15 + 1/15 x 20 +….+ 1/2005 x 2010

Comments ( 2 )

  1. N = 1/(1 × 5) + 1/(5 × 10) + 1/(10 × 15) + ………… + 1/(2005 × 2010)
    5N = 1 – 1/5 + 1/5 – 1/10 + ……………….. + 1/2005 – 1/2010
    5N = 1 – 2010 = 2009/2010
    N = 2009/2010 . 1/5 = 2009/10050

  2. Giải đáp:
     N=2411/10050.
    Lời giải và giải thích chi tiết:
    N=1/(1xx5)+1/(5xx10)+1/(10xx15)+1/(15xx20)+….+1/(2005xx2010)
    =>5N=1+5/(5xx10)+5/(10xx15)+5/(15xx20)+….+5/(2005xx2010)
    =>5N=1+1/5-1/10+1/10-1/15+1/15-1/20+….+1/2005-1/2010
    =>5N=1+1/5-1/2010
    =>5N=2411/2010
    =>N=2411/10050.

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