1/4 = 0.25 m

                              Bai   Lam

So khom hoa can trong theo chieu dai la :

5.5 : 0.25 = 22 ( khoi khom hoa )

So khom hoa can trong theo chieu rong la:

3.75 : 0.25 = 15 ( khoi khom hoa )

Tong so khom hoa tren manh vuon la:

(22+15) x 2 - 4 = 70 ( khom hoa )

 Vay so khom hoa can trong tren manh vuon la 70 khom

a) 1/5 + 4/5 : x = 0.75 

 1/5 + 4/5 : x = 3/4

4/5 : x = 3/4 - 1/5

4/5 : x = 15/20 - 3/20

4/5 : x = 12/20

x = 4/5 x 20/12

x = 12/25

a) 1/5 + 4/5 : x = 0.75

 1/5 + 4/5 : x = 3/4

          4/5 : x = 3/4 - 1/5

          4/5 : x = 15/20 - 4/20

          4/5 : x = 11/20

                  x = 11/20 : 4/5 

                  x = 11/20 x 5/4

                  x = 11/16

b) x + 1/2 = 1 - x

x + x + 1/2 = 1

2x              = 1 - 1/2

2x              = 2/2 - 1/2

2x              = 1/2

  x              = 1/2 : 2

  x              = 1/2 x 1/2

  x              = 1/4

a) 2/3 x 5/4 - 3/4 x 2/3 = 2/3 x ( 5/4 - 3/4 ) = 2/3 x 2/4 = 1/3

b) 2 x -3/2²  - 7/2 = 2 x 9/4 - 7/2 = 9/2 - 7/2 = 2/2 = 1

c) -3/4 x 5 3/15 - 0.75 x 36/13 = -3/4 x 68/13 - 3/4 x 36/13 = -3/4 x ( 68/13 + 36/13 ) = -3/4 x 104/13 = -6