${}^{40}$

 nên AOD=BOC=1/2.100=50 độ

 nên AOD=BOC=1/2.100=50 độ

ta coi tổng số học sinh lớp đó  là 1

ta có

1-[1/4+1/3]=5/12

Cách 1:

$(\frac{2}{3}\times \frac{4}{5})\times \frac{5}{6}=\frac{8}{15}\times \frac{5}{6}=\frac{8\times 5}{15\times 6}=\frac{2\times 2\times 2\times 5}{3\times 5\times 2\times 3}=\frac{4}{9}$

Cách 2:

$(\frac{2}{3}\times \frac{4}{5})\times \frac{5}{6}=\frac{2}{3}\times (\frac{4}{5}\times \frac{5}{6})=\frac{2}{3}\times \frac{4}{6}=\frac{2\times 4}{3\times 6}=\frac{2\times 4}{3\times 2\times 3}=\frac{4}{9}$

Cách 1:

$(\frac{1}{2}+\frac{1}{3})\times \frac{1}{5}=\left(\frac{3+2}{6}\right)\times \frac{1}{5}=\frac{5}{6}\times \frac{1}{5}=\frac{1}{6}$

Cách 2:

$(\frac{1}{2}+\frac{1}{3})\times \frac{1}{5}=\frac{1}{2}\times \frac{1}{5}+\frac{1}{3}\times \frac{1}{5}=\frac{1}{10}+\frac{1}{15}=\frac{3}{30}+\frac{2}{30}=\frac{5}{30}=\frac{1}{6}$

Số cam còn lại sau lần bán thứ hai là:

    [10+1] x 2 = 22 [quả]

Số cam còn lại sau lần bán thứ nhất là: 

    [22+1] x 2= 46 [quả]

Số cam lúc đầu là:

   [46+1] x 2 = 94 [quả]

Đáp số : 94 quả

Lunar New Year festival, also known as Tet, is the biggest traditional festival in my country, Viet Nam. Tet is usually from the end of January to early February. Before Tet, Vietnamese people prepare many things, we always want everything to be perfect for the new year. In particularly, we clean the house and decorate it with flowers and trees such as kumquat tree, peach blossom,… In addition, a huge amount of food will be bought before Tet for making traditional dishes like Banh Chung, Banh Tet, Gio cha,… During Tet, we visit our relatives and give them wishes. Traditionally, elders will give lucky money to children and the oldest people in the family. However, nowadays, we can give it to anyone including friends, parents, neighbors. Besides, Vietnamese usually go to pagodas or temples to pray for health, wealth, success. All in all, Tet is all about going back to origins, being good to others, enjoying the precious moment, and wishing for the best to come.