Đề vòng chung kết Quốc gia kỳ thi Olympic toán học Quốc tế TIMO 2020-2021 Khối 4 (Kèm đáp án)

 THAILAND INTERNATIONAL 
 MATHEMATICAL OLYMPIAD 
 FINAL ROUND 2020 – 2021 
 Primary 4 
 Time allowed: 120 minutes 
 Question Paper 
 Instructions to Contestants: 
1. Each contestant should have ONE Question-Answer Book which CANNOT be 
 taken away. 
2. There are 5 exam areas and 6 questions in each exam area. There are a total of 30 
 questions in this Question-Answer Book. Each question carries 5 marks. Total 
 score is 150 marks. No points are deducted for incorrect answers. 
3. All answers should be written on ANSWER SHEET. 
4. NO calculators can be used during the contest. 
5. All figures in the paper are not necessarily drawn to scale. 
6. Write down the answer in the simplest form. If the calculation result is a fraction, 
 please write down the answer as a proper or mixed fraction, decimal figure is also 
 accepted. Marks will NOT be given for incorrect unit. 
7. This Question-Answer Book will be collected at the end of the contest. 
 DO NOT turn over this Question-Answer Book without approval of the examiner. 
 Otherwise, contestant may be DISQUALIFIED. 
 1 
 All answers should be written on the ANSWER SHEET. 
9. Find the value of 9 11 13 15. 
10. Find the value of 208 222 236 250 ... 530 544 . 
11. Find the value of 592 23 12  23 97  23 174  23. 
12. Using method SSS 2 , find the value of S 7 14 28 ... 1792 3584. 
 Number Theory 
13. If a 10-digit number 202AB 89293 is divisible by 28 and BA 0 , find the value of A. 
14. The sum of 9 consecutive even numbers is 1494. Find the largest number. 
15. The product of positive numbers A and B is 1014. A is 6 times of B. Find the value of A. 
16. Define the operation symbol a b ()()() b a a b a a b , find the value of 
 6 8 29 . 
17. Find the unit digit of A if A 333...3 4 4 4... 4 7 7 7 ...7 . 
 2021's 2021' s 2021' s
18. What is the largest 3-digit number that can be divisible by 21 and 45? 
 Geometry 
19. How many rectangle(s) is / are there in the figure below? 
 Question 19 
20. It is given that the area of a rectangle is 336. The width and length are integers. Find the 
 minimum value of the perimeter. 
21. The figure on the left is a small right-angled triangle with side length 8 and hypotenuse 10. 
 The large triangle on the right is formed by 4 identical small right-angled triangles. Find 
 the area of the large triangle on the right. 
 Question 21 
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