HEXAGON. Singapore-Asia Pacific Mathematical Olympiad for Primary Schools (Mock Test for APMOPS 2012) Pham Van Thuan

Transcription

1 HEXAGON inspiring minds always Singapore-Asia Pacific Mathematical Olympiad for Primary Schools (Mock Test for APMOPS 2012) Practice Problems for APMOPS 2012, First Round 1 Suppose that today is Tuesday. What day of the week will it bee 100 days from now? 2 Ariel purchased a certain amount of apricots. 90% of the apricot weight was water. She dried the apricots until just 60% of the apricot weight was water. 15 kg of water was lost in the process. What was the original weight of the apricots (in kg)? 3 Notice that 1 2 = 1, 1 (2 3) = 2, and 1 (2 (3 4)) = 2. What is the value of 1 (2 (3 ( )))...)? 4 You are preparing skewers of meatballs, where each skewer has either 4 or 6 meatballs on it. Altogether you use 32 skewers and 150 meatballs. How many skewers have only 4 meatballs on them? 5 The numbers 1, 2, 3,..., 100 are written in a row. We first remove the first number and every second number after that. With the remaining numbers, we again remove the first number and every second number after that. We repeat this process until one number remains. What is this number? 6 P and Q are whole numbers so that the ratio P : Q is equal to 2 : 3. If you add 100, 200 to each of P and Q, the new ratio becomes equal to 3 : 4. What is P? Copyright c 2012 HEXAGON 1

2 7 The following figure consists of 3 smaller rectangles and a hexagon whose areas are 18 cm 2, 80 cm 2, 28 cm 2, and 61 cm 2. If all the side-lengths in centimetre of the rectangles and the hexagon are integers, find the area of the shaded region Suppose that a, and b are positive integers, and the four numbers a + b, a b, a b, a b are different and are all positive integers. What is the smallest possible value of a + b? 9 You are given a two-digit positive integer. If you reverse the digits of your number, the result is a number which is 20% larger than your number. What is your number? 10 The number N = consists of 2006 ones. It is exactly divisible by 11. How many zeros are there in the quotient N 11? 11 This mock test, prepared by Thuận from HEXAGON centre in Hanoi, consists of 30 problems. Pupil A gets a score that is an odd multiple of 5 and pupil B gets a score that is a even multiple of 7. The mark of each problem is an integer and each of the two pupils score is an integer the difference of which is 3 and sum is less than 100. Find the higher score of the pupils. 12 In a large hospital with several operating rooms, ten people are each waiting for a 45 minute operation. The first operation starts at 8:00 a.m., the second at 8:15 a.m., and each of the other operations starts at 15 minute intervals thereafter. When does the last operation end? 13 Each of the integers 226 and 318 have digits whose product is 24. How many three-digit positive integers have digits whose product is 24? 2

3 14 A work crew of 3 people requires 20 days to do a certain job. How long would it take a work crew of 4 people to do the same job if each of both crews works at the same rate as each of the others? 15 Each of the nine numbers 1, 2,..., 9 is to be placed inside the cell of the following 3 3 grid once. The product of three numbers in each row and in each column is given: the product of numbers in the first column is 35, the second column is 96, the product of three numbers in the first row is 54, etc. Find the value of p + q p q N is a whole number greater than 2. The six faces of a 5 5 N block of wood are painted red and then the block cut into 25 N1 1 1unit cubes. If exactly 92 unit cubes have exactly two faces painted red, what is N? 17 Eleven people are in a room for a meeting. When the meeting ends, each person shakes hands with each of the other people in the room exactly once. The total number of handshakes that occurs is x. Find the value of x 18 Mark has a bag that contains 3 black marbles, 6 gold marbles, 2 purple marbles, and 6 red marbles. Mark adds a number of white marbles to the bag and tells Susan if she now draws a marble at random from the bag, the probability of it being black or gold is 3 7. The number of white marbles that Mark adds to the bag is n. Find the value of n. 19 A number line has 40 consecutive integers marked on it. If the smallest of these integers is 11, what is the largest? 20 If I add 5 to 1 3 of the number, the result is 1 2 of the number. What is the number? 21 If n is a positive inter such that all the following numbers are prime, find the value of n. 5n 7, 3n 4, 7n + 3, 6n + 1, 9n

4 22 The diagram below shows a trapezium with base AB and CD, ABC = 55. E is inside the trapezium such that AE bisects angle BAD and ED bisects angle ADC. If the measure of DAE is x, find the value of x. A 55 B E D C 23 Let a denote the integer not exceeding a. If n is a whole number, n 2, find p p = n 2 n. 24 How many numbers are there that appear both in the arithmetic sequence 10, 16, 22, 28,..., 1000 and the arithmetic sequence 10, 21, 32, 43,..., 1000? 25 The whole numbers from the set {1, 2, 3,..., 2020} are arranged in the following manner What is the number that will appear directly below the number 2012? 26 In triangle ABC, produce a line from B to AC, meeting at D, and from C to AB, meeting at E. Let BD and CE meet at X. Let triangle BXE have area 4 cm 2, triangle BXC have area 8, and triangle CXD have area 10. Find the area of quadrilateral AEXD. A E D X B C 4

5 27 The length of a rectangle is 1 cm more than twice its width. If the perimeter of the rectangle is 74 cm, what is the area of the rectangle? 28 At Maths Project Olympiad, prize money is awarded for 1st, 2nd and 3rd places in the ratio 3 : 2 : 1. Last year John and Ashley shared third prize equally. What fraction of the total prize money did John receive? 29 A goat is tied to one of the corners of a rectangular barn on a rope that is 50 feet long. The dimensions of the barn are 40 feet by 30 feet. Assuming that the goat can graze wherever its rope allows it to reach, what is the square footage of the grazing area for the goat? 30 Find a nine-digit positive integer, d 1 d 2 d 3 d 4 d 5 d 6 d 7 d 8 d 9 with distinct digits, so that 1 divides d 1, 2 divides d 1 d 2, 3 divides d 1 d 2 d 3,..., 8 divides d 1 d 2 d 3 d 4 d 5 d 6 d 7 d 8, and 9 divides d 1 d 2 d 3 d 4 d 5 d 6 d 7 d 8 d 9. Only digits 1, 2,..., 9 are to be used. 5

6 Answer Key Question Answer Question Answer Question Answer 1 Thursday AM m π