Chu vi hình chữ nhật là: (5,5 + 3,75) . 2 = 18,5 (m)

             Số khóm hoa cần trồng là: 18,5 : 1/4 - 4 = 70 (khóm hoa)

 

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

4/5 : x = 11/20

        x = 4/5 : 11/20

        x = 16/11

b) 2x = 1  - 1/2

     2x = 1/2

        x = 1/4

a) 2/3 . (5/4 - 3/4)

= 2/3 . 2/4

= 2/3 . 1/2

= 1/3

b) 2 . (9/4) - 7/2

= 18/4 - 7/2

= 1

c) -3/4 . ₅3/13 - 3/4 . 36/13

= -3/4 . ( 68/13 + 36/13 )

= -3/4 . 8

= -6

Đăng lên FB hay nè

Minh Phuc

Ngoc Lang village, Binh Ngoc commune, Tuy Hoa city, Phu Yen Province

Mr.Truong

Tuy Hoa city, Phu Yen Province

Dear Mr.Truong

My name is Phuc and I am in Class 7B. I am writing to ask you to provide us with better food in the cafeteria.

At the moment, the cafeteria only have salad, vegetables and rice. It's not enough good for everyone. It doesn't fell delicious. 

I think the cafeteria should sell things like grill foods, fried and hot pot food. They are so much better for us and will help us study better and feel healthier.

Please help make the cafeteria healthier.

Sincerely,

Minh Phuc

a) 2 . x = 1/5

x = 1/5 : 2 

x = 1/10

b) (-8/5 + x) . 13/12 = 13/6

(-8/5 + x) = 13/6 : 13/12 

(-8/5 + x) = 13/6 . 12/13 = 2

x = 2 + 8/5

x = 18/5

c) (x : 7/3) . 1/7 = -3/8

(x . 3/7) = -3/8 : 1/7 

x . 3/7 = -3/8 . 7/1 = -21/8

x = -21/8 : 3/7

x = -21/8 . 7/3

x = -49/8

d) -4/7 . x + 7/5 = -3/40

-4/7 . x = -3/40 - 7/5

-4/7 . x = -59/40

x = -59/40 : -4/7

x = -59/40 . -7/4

x = 413/160 

a) x = 7 + 1,62 - 2/5

x = 8,62 - 0,4

x = 8,22

b) x = 23/5 + 1/5 - 1/2

= 46/10 + 2/10 - 5/10

= 43/10

c) -x + 2x = 3/5 + 4/7

x = 21/35 + 20/35

x = 41/35

d) x = 7/2 - 5/7 + 1/13 - 1/4

= 13/4 - 5/7 + 1/13

= 71/28 + 1/13 

= 923/364 + 28/364 

= 951/364

a) A = 2/7.(1/4 - 1/3) : 2/7.( 3/9 - 2/5)

= -1/12 :  -3/45

= -1/12 . -45/3

= 45/36 

= 5/4

b) Tử số: 3/4 . ( 1/5 - 2/7 - 1/3 + 2/7) = 3/4 . -2/15 = -1/10

Mẫu số: 1/5 . (2/7 + 3/9) - 1/3 . ( 2/7 + 3/9) = (2/7 + 3/9). (1/5 - 1/3) = 13/21 . -2/15 = -26/315 

B = -1/10 : -26/315 = -1/10 . -315/26 = 63/52

a) A = 3/5 . 6/7 + 3/7 . 3/5 - 2/7 . 3/5 

= 3/5.(6/7 + 3/7 - 2/7)

= 3/5 . 1

= 3/5

b)  B = (-13. 2/5 + -2/9 . 2/5 + 2/5 . 11/9) . 5/2

= 2/5.(-13 + -2/9 + 11/9) . 5/2

= 2/5. -12 . 5/2

= -24/5 . 5/2

= -12

c) C = (-4/5 + 5/7) . 3/2 + (-1/5 + 2/7) . 3/2

= 3/2.[(-4/5 + -1/5) + (5/7 + 2/7)] 

= 3/2 [-1 + 1]

= 3/2 . 0

= 0

d) D = 4/9 : ( 1/15 - 2/3) + 4/9 : (1/11 - 5/22)

= 4/9: [(1/15 - 10/15) + ( 2/22 - 5/22)]

= 4/9 : [-9/15 + -3/22]

= 4/9 : [-3/5 + -3/22)

= 4/9 : [ -66/110 + -15/110 ]

= 4/9 :  -81/110

= 4/9  . -110/81

= 440/729

 

a) P = 2/3 + 1/4 + 3/5 - 7/45 + 5/9 + 1/12 + 1/35

= 8/12 + 3/12 + 1/12 + 27/45 - 7/45 + 25/45 + 1/35

= 1 + 1 + 1/35 

=  2 + 1/35

b) Q = 5 - 3/4 + 1/5 - 6 - 7/4 + 8/5  - 2 + 5/4 - 16/5

= (5 - 6 - 2) + (-3/4 - 7/4 + 5/4) + (1/5 + 8/5 - 16/5) 

= -(3 + 5/4 + 7/5) = -113/20