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

Toán Lớp 6: B=5/1.4 + 5/4.7 + … + 5/100 + 103

Toán Lớp 6: B=5/1.4 + 5/4.7 + … + 5/100 + 103

Comments ( 2 )

  1. B= \frac{5}{1.4} + \frac{5}{4.7} + …. + \frac{5}{100.103}
    = 5/3 . ( \frac{3}{1.4} + \frac[3}{4.7} + … + \frac{3}{100.103})
    = 5/3 . ( 1 – 1/4 + 1/4 – 1/7 + … + 1/100 – 1/103)
    = 5/3 . ( 1 – 1/103)
    = 5/3 . 102/103
    = 170/103
    Vậy B = 170/103

  2. B = 5/( 1 . 4 ) + 5/( 4 . 7 ) + …. + 5/( 100 . 103 )
    B = 5/3 . ( 3/( 1 . 4 ) + 3/( 4 . 7 ) + …. + 3/( 100 . 103 ) )
    B = 5/3 . ( 1/1 – 1/4 + 1/4 – 1/7 + …. + 1/100 – 1/103 )
    B = 5/3 . ( 1 – 1/103 )
    B = 5/3 . 102/103
    B = 170/103

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