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

Toán Lớp 5: a, Tính 3/7+5/8=–… 4/9+7/18=-… 59/56-5/8=–.. 5/6-4/9 ==…

Toán Lớp 5: a, Tính
3/7+5/8=……….. 4/9+7/18=……. 59/56-5/8=………. 5/6-4/9 =…………… 1/2+1/3+1/4=………… 13/12-(1/2+1/3)
b , Tính nhẩm
2/7+3/7=……. 3/5+2=…………. 2 3/5-2=…………. 2-3/5=……………..
c , Tính bằng cách thuận tiện nhất
2/5+3/4+1/4=……………………………….
30/4-6/8-15/20=………………………………………..

Comments ( 2 )

  1. a, Tính
    3/7+5/8                                      4/9+7/18
    = 24/56 + 35/56                        = 8/18 + 7/18
    = 59/56                                      = 15/18 = 5/6
    59/56 – 5/8                                5/6 – 4/9 
    = 59/56 – 35/56                        = 15/18 – 8/18
    = 24/56 = 3/7                           = 7/18
    1/2+1/3+1/4                            13/12-(1/2+1/3)
    = 6/12+4/12+ 3/12                 = 13/12- ( 6/12 + 4/12 )
    = 13/12                                     = 13/12- 10/12
                                                       = 3/12 = 1/4
    b , Tính nhẩm
    2/7+3/7=5/7                            
    3/5-2= -7/5(âm 7/5)
    3/5+2= 13/5
    2-3/5= 7/5
    c , Tính bằng cách thuận tiện nhất
    2/5+3/4+1/4
    = 2/5+(3/4+1/4)
    = 2/5 +1
    = 7/5
    30/4 – 6/8 -15/20
    =(30/4 – 6/8) -15/20
    =27/4 – 3/4
    = 24/4= 6

  2. a,tính
    _3/7+5/8=35/56+15/56=50/56
    _4/9+7/18=8/18+7/18=15/18
    _59/56-5/8=59/56-35/56=24/56
    _1/2+1/3+1/4=6/12+4/12+3/12=13/12
    _5/6-4/9=45/54-24/54=21/54
    _13/12-(1/2+1/3)= 13/12-5/6=13/12-10/12=3/12
    b,tính  nhẩm
    2/7+3/7=5/7                        3/5+2=13/5
    3/5-2 (3/5 <1 làm  sao  trừ  2 đc)            2-(3/5)=7/5
    c,
    2/5+3/4+1/4=2/5+1=7/5
    30/4-6/8-15/20=30/4-3/4-3/4=21/4
     

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

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