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

Toán Lớp 4: tính nhanh:2/7×1/5+2/7×3/10+1/2×2/7 136×75+136×19+5×136+136 1/2+1/4+1/8+=..+1/64+1/128+1/126 1/1×2+1/2×3+1/3×4+1/4×5+-…

Tháng Mười Một 15, 2022 Toán học 2 Comments 0 views

Toán Lớp 4: tính nhanh:2/7×1/5+2/7×3/10+1/2×2/7
136×75+136×19+5×136+136
1/2+1/4+1/8+…………..+1/64+1/128+1/126
1/1×2+1/2×3+1/3×4+1/4×5+………+1/99×100
2×2/4+2/4×6+2/6×8+……..+2/98×100
2/1×3+2/3×5+2/5×7+…….+2/97×99

Comments ( 2 )

  1. tongtung
    tongtung
    15 Tháng Mười Một, 2022 at 10:06 chiều
    Reply
    Giải đáp:
     
    Lời giải và giải thích chi tiết:
    a, 2/7 × 1/5 + 2/7 × 3/10 + 1/2 ×2/7
    = 2/7 × ( 1/5 + 3/10 + 1/2 )
    = 2/7 × 1
    = 2/7
    ___________
    b, 136 × 75 + 136 × 19 + 5 × 136 + 136
    = 136 × ( 75 + 19 + 5 + 1 )
    = 136 × 100
    = 13600
    ___________
    c, 1/2 + 1/4 + 1/8 +………+ 1/64 +1/128
    = 1 – 1/2 + 1/2 – 1/4 + 1/4 – 1/8 +………..+ 1/32 – 1/64 + 1/64 – 1/128
    = 1 – 1/128
    = 127/128
    ___________
    d, 1/(1×2) + 1/(2×3) +……….+ 1/(99×100)
    = 1 – 1/2 + 1/2 – 1/3 +……..+ 1/99 – 1/100
    = 1 – 1/100
    = 99/100
    ___________
    e, 2/(2×4) + 2/(4×6) +………….+ 2/(98×100)
    = 1/2 – 1/4 + 1/4 – 1/6 +……………+ 1/98 – 1/100
    = 1/2 – 1/100
    = 49/100
    ___________
    i, 2/(1×3) + 2/(3×5) +…………..+ 2/(97×99)
    = 1 – 1/3 + 1/3 – 1/5 +………….+ 1/97 – 1/99
    = 1 – 1/99
    = 98/99 

  2. lantrungbach
    lantrungbach
    15 Tháng Mười Một, 2022 at 10:06 chiều
    Reply
    2/7 × 1/5 + 2/7 × 3/10 + 1/2 × 2/7
    = 2/7 × ( 1/5 + 3/10 + 1/2 )
    = 2/7 × 1
    = 2/7
    —
    136 × 75 + 136 × 19 + 5 × 136 + 136
    = 136 × ( 75 + 19 + 5 + 1 )
    = 136 × 100
    = 13600
    —
    1/2 + 1/4 + 1/8 + … + 1/64 + 1/128 ( thừa 1/126 )
    = 1 – 1/2 + 1/2 – 1/4 + 1/4 – 1/8 + … + 1/64 – 1/128
    = 1 – 1/128
    = 127/128
    —
    1/{1 × 2} + 1/{2 × 3} + 1/{3 × 4} + … + 1/{99 × 100}
    = 1/1 – 1/2 + 1/2 – 1/3 + 1/3 – 1/4 + … + 1/99 – 1/100
    = 1/1 – 1/100
    = 99/100
    —
    2/{2 × 4} + 2/{4 × 6} + 2/{6 × 8} + … + 2/{98 × 100}
    = 1/2 – 1/4 + 1/4 – 1/6 + 1/6 – 1/8 + … + 1/98 – 1/100
    = 1/2 – 1/100
    = 49/100
    —
    2/{1 × 3} + 2/{3 × 5} + 2/{5 × 7} + … + 2/{97 × 99}
    = 1/1 – 1/3 + 1/3 – 1/5 + 1/5 – 1/7 + … + 1/97 – 1/99
    = 1/1 – 1/99
    = 98/99
    #dtkc

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

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