Đề vòng chung kết Quốc gia kỳ thi Olympic toán học Quốc tế TIMO 2020-2021 Khối 5 (Kèm đáp án)

 THAILAND INTERNATIONAL 
 MATHEMATICAL OLYMPIAD 
 FINAL ROUND 2020 – 2021 
 Primary 5 
 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. 
 1 1 1 1 1
12. Find the value of ... . 
 13 15 15 17 17 19 33 35 35 37
 Number Theory 
13. If a 10-digit number 20216AB 893 is divisible by 36 and A 5 , find the value of 
 AB . 
14. Find the number of all positive factors of 588. 
15. Find the unit digit of A if 
 A 2468 2468 2468 ... 2468 106 106 ... 106 22 22 ... 22 . 
 2021's 2022' s 2023' s
16. Define the operation symbol: 
 4222 
 42 
 42 
 5322 
 53 
 53 
 9622 
 96 
 96 
 Find the value of (6 3) (8  5) . 
17. The sum of 13 consecutive odd numbers is 1183. Find the largest number. 
18. The sum of A and B is 693. A is 62 times of B. Find the value of A. 
 Geometry 
19. Now there are 11 points. How many quadrilateral(s) can be formed? 
20. How many rectangle(s) with both 2 “*” is / are there in the figure below? 
 * 
 * 
 3