Combinatorics
21. 15 students join a competition. Only top 5 students can be promoted to next round. How many different way(s) of promotion advance is / are there?
Different way: Cách khác nhau.

22. It is known that there are 8 classes of grade 5 in a primary school. At least how many students are there in grade 5 to ensure there exist 41 students in the same class?
At least: Ít nhất; Ensure: Chắc chắn; Exist: Tồn tại.

23. Choose 3 digits from 1, 2, 3, 4, 6, 8 and 0 to form 3-digit numbers. How many even number(s) greater than 300 is / are there? (The repetition of digits is not allowed)
Digit: Chữ số; 3-digit number: Số có 3 chữ số; Even number: Số chẵn; Greater than: Lớn hơn; Repetition of digits is not allowed: Các chữ số không được lặp lại.

24. A flight of stairs has 10 steps. Peter can go up for 1 step, 2 steps or 3 steps each time. How many way(s) is / are there for Peter to go up the stairs?
Step: Bước; Way: Cách.

25. Numbers are drawn from 80 integers 20 to 99. At least how many number(s) is / are drawn at random to ensure that there are two numbers whose sum is 85?
Integer: Số nguyên; At least: Ít nhất; Random: Ngẫu nhiên; Ensure: Chắc chắn; Sum: Tổng.
~ End of Paper ~

Question 1:
Compare: 

Question 2:
Compare: A =  and B = 
Answer: A  B

Fill in the blank with the suitable number

Question 3:
Calculate: 
The value of A is 

Question 4:
Calculate: 
The value of A is 

Question 5:
Find two consecutive even numbers if the first number is  of the second number.
Answer: The second number is 

Question 6:
There are 49 students in a class. Boy students are  the number of girl students. There are  girl students in this class.

Question 7:
How many natural numbers not greater than 1665 which are divisible by 5?
Answer:  numbers

Question 8:
Calculate: 
The value of A is 

Question 9:
How many 3 - digit numbers are divisible by 2, 3 and 5?
Answer:  numbers.

Question 10:
If  then  is 

Question 1: What is 1/6 of  744? Answer: 124
Question 2: Express seventy thousand, four hundred and nine in numerals. Answer: 70409 
Question 3: Study the pattern. 88:8=11   880:8=110  8800:8= ?  The missing number is 1100
Question 4: Subtract 346 from 752. Answer: 406
Question 5: The ratio of boys to girls at a school is 5:4. If there are 255 boys at the school then how many students are there at the school?  Answer: 459 students.
Question 6: The product of  2 different natural numbers is 9. Their sum is 10 
Question 7: Jack, Mary and Jacob buy ice creams. Jack buys twice as many as Mary. Jacob buys three times as many as Jack. If Jacob buys 12 ice creams then Mary buys 2 ice creams.
Question 8: My giant flower doubles its size every day. On Friday, it is 5 ( hay 10 gì đó ) times as big as its was on the preceding Sunday.
Question 9: If we write all of the whole numbers from 10 through 99 and cross out any number in which the first or second digit is divisible by 2 (for example, 41 is crossed out as 4 is divisible by 2 and 36 is crossed out as 6 is divisible by 2), how many numbers are crossed out? Answer: 65 numbers.
Question 10: It takes Bella three hours to clean a house. It takes Anna two hours to clean the house. How long would it take for them to clean it together?  Answer: 72 minutes.

Fill in the blank with the suitable number

Question 1:
There are 49 students in a class. Boy students are  the number of girl students. There are  girl students in this class.

Question 2:
Calculate: 
The value of A is 

Question 3:
Calculate: 
The value of A is 

Question 4:
Jessica is 8 years old. Her grandmother is  of her age. How old is Jessica's grandmother?
Answer:  years old.

Question 5:
If the sum of denominator and numerator of a fraction is 52 and the denominator is 18 units more than the numerator then the numerator is 

Question 6:
Find two consecutive even numbers if the first number is  of the second number.
Answer: The second number is 

Question 7:
Calculate: 
The value of A is 

Question 8:
How many natural numbers not greater than 1665 which are divisible by 5?
Answer:  numbers

Question 9:
If  then  is 

Question 10:
The sum of three consecutive even numbers is 960. The greatest numbers is