\(\dfrac{1}{2}.3+\dfrac{2}{3}.5+\dfrac{4}{5}.9+\dfrac{1}{9}.10\)

\(\dfrac{3}{2}+\dfrac{10}{3}+\dfrac{36}{5}+\dfrac{10}{9}\\ \dfrac{29}{6}+\dfrac{374}{45}=\dfrac{1183}{90}\)

(6,45 + 3,55) x 2,15

10 x 2,15 = 21,5

science : khoa hojc

vietnamese : tiếng việt 

literature : ngữ văn

math : toán

biology : sinh học

history : ljch sử

pe : giáo dục thể chất

it : tin học

english : tiếng anh

music : aam nhạc

geography : địa lí

art : mỹ thuật

a) my uncle lives in 75 Ly Thuong Kiet Street.

=> my uncle lives on 75 Ly Thuong Kiet Street.

b) my father go fishinf once a week.

=> my father goes fishing onece a week 

c) He wash his face every day.

=> He washes his face every day

d) my parents visits ny grandparents once a week.

=> my parents visit my grandparents once a week.

e) what does he study after school?-He study in the library.

what does he study after school?-He studies in the library

nga goes to school on foot every morning and she goes home at four thirty in the afternoon

\(x:3+4,5\)\(=10\)

\(x:3=10-4,5\\ x:3=5,5\)

\(x=5,5\cdot3\)

\(x=16,5\)

vậy x = 16,5

23,72 ha = 2 372 000 000 cm2
783,2 m2 = 7 832 000 cm2
3,826 m2 = 38 260 000 cm2
6,92 dm2 = 692 cm2
73 m2= 730 000 cm2
6,62 hg = 662 g
5,5 kg =  5500 g
62,873 dag = 628,73 g
5,3 kg = 5300  g
72,002 dag = 720,02 g

do bài này nhiều quá nên có j sai cho mình xin lỗi nha !

cách tính nhanh nhất là lấy máy tính bấm : 

125 . 32 + 25 . 16

= 125 . 16 . 2 + 25 . 16

= (125 . 2) . 16 + 25 . 16

=         250 . 16 + 25 . 16

= 16 . (250 + 25)

= 16 . 275 = 4400