5ª) Resolva as operações com frações abaixo? ????) 2/5+3/6+1/2= B)2/3-1/5= C)3/6×1/4= D)6/7÷2/3=

dica:

NUMA EXPRESSÃO NUMÉRICA faz :

(1º) dentro dos ( ) parenteses

SOMA e SUBTRAÇÃO de fração faz mmc

Resolva as operações abaixo:

a) (1/3 + 2/5)

  1       2

(------ +-------) mmc 3,5I 3

  3      5               1,5I 5

                              1,1 = 3x5 = 15

   5(1) + 3(2)              5 + 6                11

(-----------------------) = (----------------) = -----------

         15                       15                  15

b) 7/4 .(9/3 - 1/4) veja

7         9         1

-----.(---------- - -------) mmc 3,4I 2

4        3         4               3,2I 2

                                         3,1I 3

                                         1,1/ = 2x2x3 = 12

7          4(9) - 3(1)

-------.(------------------)

4              12

 7          36 - 3

--------.(-------------)

 4          12

 7      33

--------.(------)    ==> (.) esse pontinho é MULTIPLICAÇÃO

 4       12

7x33              231                             231: 3          77

----------- = -------------- = simplifique = --------- = --------------

4x12                 48                              48: 3         16

c) 2/3 + 1/6 - 1/4

2          1            1  mmc 3,6,4I 2

-------- + ------- - -------         3,3,2I 2

 3          6         4             3,3,1I 3

                                          1,1,1/ = 2x2x3 = 12

4(2) + 2(1) - 3(1)

---------------------

       12

8 + 2 - 3          10 - 3             7

--------------- = --------------- = --------

    12                12                12

d) (7/6 + 2/5). 1/6  veja

 7         2       1

(------ + --------)------ mmc 6,5I 2

 6       5        6             3,5I 3

                                        1,5I 5

                                        1,1/ = 2x3x5 = 30

 5(7) + 6(2)    1

(-----------------)-------

     30           6

 35 + 12    1

(------------)--------

     30

     42        1

------------x--------

     30      6

42x1           42                             42: 6              7

----------- = ------------ simplifique = --------- =     ---------- 

30x6         180                             180: 6           30

e) (7/8 + 1/5). 1/3 veja

 7      1       1

(----- + ------)----- mmc 8,5I 2

 8      5     3            4,5I 2

                                  2,5I 2

                                  1,5I 5

                                   1,1/ = 2x2x2x5 = 40

 5(7) + 8(1)    1

(--------------)------

     40         3

  35 +8    1

(-----------)----

    40      3

   43        1

----------x-------

  40      3

43x1            43

---------- = ---------

40x3         120