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

Toán Lớp 6: Bài 1 tính nhanh a}1/21+2/21+3/21+4/21+5/21+-..+17/21+18/21+19/21+20/21 b}1/10+20/100+300/1000+4000/10000 c} 4/3×7 + 4/7×11 + 4/11×5

Toán Lớp 6: Bài 1 tính nhanh
a}1/21+2/21+3/21+4/21+5/21+……+17/21+18/21+19/21+20/21
b}1/10+20/100+300/1000+4000/10000
c} 4/3×7 + 4/7×11 + 4/11×5 + 4/15×19 + 4/19×23 + 4/23×27
BÀi 2 tính nhanh
a} 4823+1560+5177+8440
b} 10556+8074+9444+926+1000
c} 576+789+467+111
Bài 3 tính nhanh
21,251+6,058+0,749+1,042
1,53+5,039+12,47+5,691

Comments ( 2 )

  1. Bài 1:
    a) 1/21+2/21+3/21+4/21+5/21……+17/21+18/21+19/21+20/21
    = (1+2+3+….+19+20)/21
    = ((20+1) . [(20-1) : 1 + 1] : 2)/21
    = 210/21
    = 10
    b) 1/10+20/100+300/1000+4000/10000
    = 1/10 + 2/10 + 3/10 + 4/10
    = (1+2+3+4)/10
    = 10/10
    = 1
    c) 4/(3.7) + 4/(7.11) + 4/(11.15) + 4/(15.19) + 4/(19.23) + 4/(23.27)
    = 1/3 – 1/7 + 1/7 – 1/11 +1/11 – 1/15 + 1/15 – 1/19 + 1/19 – 1/23 + 1/23 – 1/27
    = 1/3 – 1/27
    = 9/27 – 1/27
    = 8/27
    Bài 2: 
    4823+1560+5177+8440
    = (4823+5177)+(1560+8440)
    = 10000 + 10000
    = 20000
    10556+8074+9444+926+1000
    = (10556+9444)+(8074+926)+1000
    = (10556+9444)+(8074+926)+1000
    = 20000 + 9000 + 1000
    = 30000
    576+789+467+111
    = 576+789+(467-43)+111+43
    = 576+789+424+111+43
    = (576+424)+(789+111) + 43
    = 1000+900 + 43
    = 1943
    Bài 3: 
    21,251+6,058+0,749+1,042
    = (21,251 + 0,749) +(6,058+1,042)
    = 22 + 7,1
    = 29,1
    1,53+5,039+12,47+5,691
    = (1,53 + 12,47) + (5,691 – 0,73) + 5,039 + 0,73
    = 14 + (4,961 + 5,039) + 0,73
    = 14 + 10 + 0,73
    = 24,73
    (Chúc bạn học tốt)
     

  2. Giải đáp:
     
    Lời giải và giải thích chi tiết:
     ở hình nhé

    toan-lop-6-bai-1-tinh-nhanh-a-1-21-2-21-3-21-4-21-5-21-17-21-18-21-19-21-20-21-b-1-10-20-100-300

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

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