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

Toán Lớp 7: thực hiện phép tính : a,-2/3+ 3/4 +-1/6 +-2/5 b,-2/3 + -1/5 +3/4 – 5/6 – (-7/10) c, 1/2 – -2/5 + 1/3 + 5/7 – -1/6 + -4/35 + 1/41 d, 1/

Toán Lớp 7: thực hiện phép tính :
a,-2/3+ 3/4 +-1/6 +-2/5
b,-2/3 + -1/5 +3/4 – 5/6 – (-7/10)
c, 1/2 – -2/5 + 1/3 + 5/7 – -1/6 + -4/35 + 1/41
d, 1/100.99 – 1/99.98 – …..- 1/3.2 – 1/2.1

Comments ( 2 )

  1. a, -2/3 + 3/4 + (-1/6) + (-2/5)
    = -2/3 + 3/4 -1/6 -2/5
    = -40/60 + 45/60 – 10/60 – 24/60
    = -29/60
    b,  – 2/3 + (-1/5) + 3/4 – 5/6 – (-7/10)
    = -2/3 – 1/5 + 3/4 – 5/6 + 7/10
    = -40/60 – 12/60 + 45/60 – 50/60 + 42/60
    = -15/60
    = -1/4
    c, 1/2 – (-2/5) + 1/3 + 5/7 – (-1/6) + (-4/35) + 1/41
    = 1/2 + 2/5 + 1/3 + 5/7 + 1/6 – 4/35 + 1/41
    = (1/2+1/3+1/6) + (2/5+5/7-4/35) + 1/41
    = 1 + 1 + 1/41
    = 83/41
    d, 1/(100.99) – 1/(99.98) – …..- 1/(3.2) – 1/(2.1)
    = – [1/(1×2) + 1/(2×3) + ….. + 1/(99×100)]
    = -(1-1/2+1/2-1/3+1/3-1/4+…..+1/98-1/99+1/99-1/100)
    = – (1-1/100)
    = -99/100
     

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

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