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

Toán Lớp 6: 1, tính a,2/2.4+2/4.6+2/6.8+-..+2/100.102 b,3/1.4+3/4.7+3/7.10+-.+3/31.40 c,1/2.5+1/5.8+1/8.11+-.+1/62.65 nhanhhhhhhhhhhhhhhh

Toán Lớp 6: 1, tính
a,2/2.4+2/4.6+2/6.8+……+2/100.102
b,3/1.4+3/4.7+3/7.10+…..+3/31.40
c,1/2.5+1/5.8+1/8.11+…..+1/62.65
nhanhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

Comments ( 2 )

  1. Giải đáp + Lời giải và giải thích chi tiết:
     1. Tính
    a, 2/(2.4) + 2/(4.6) + 2/(6.8) + …. + 2/(100.102)
    = 1/2 – 1/4 + 1/4 – 1/6 + 1/6 – 1/8 + … + 1/100 – 1/102
    = 1/2 – 1/102
    = 51/102 – 1/102
    = 50/102 = 25/51
    b,  Sửa đề : 3/(1.4) + 3/(4.7) + 3/(7.10) + … + 3/(37.40)
    = 1 – 1/4 + 1/4 – 1/7 + 1/7 – 1/10 + … + 1/37 – 1/40
    = 1 – 1/40
    = 40/40 – 1/40
    = 39/40
    c, 1/(2.5) + 1/(5.8) + 1/(8.11) + … + 1/(62.65)
    = 1/3 . ( 3/(2.5) + 3/(5.8) + 3/(8.11) + …. + 3/(62.65) )
    = 1/3 . (1/2 – 1/5 + 1/5 – 1/8 + 1/8 – 1/11 + … + 1/62 – 1/65)
    = 1/3 . (1/2 – 1/65)
    = 1/3 . ( 65/130 – 2/130)
    = 1/3 . 63/130
    = 21/130
     

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

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