2021 澳洲 AMC B-UpperPrimary 真题 答案 详解

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中英双语真题

2021 AUSTRALIAN MATHEMATICS COMPETITION
UPPER PRIMARY

Upper Primary Division
1-10 Questions 1 to 10, 3 marks each

1. This Nigerian flag is white and green. What fraction of it is green?
   (A) one-third (B) one-quarter (C) one-half (D) two-fifths (E) two-thirds

2. Which number makes this number sentence true?
   □ - 5 = 9
   (A) 0 (B) 4 (C) 12 (D) 9 (E) 14

3. What is the perimeter of the quadrilateral shown?
   (A) 13 cm (B) 15 cm (C) 17 cm (D) 19 cm (E) 21 cm

4. Which of the following decimal numbers has the smallest value?
   (A) 0.0002 (B) 0.002 (C) 0.02 (D) 0.2 (E) 2.0

英文真题

2021 AUSTRALIAN MATHEMATICS COMPETITION
UPPER PRIMARY

Upper Primary Division
Questions 1 to 10, 3 marks each

1. This Nigerian flag is white and green. What fraction of it is green?
   (A) one-third (B) one-quarter (C) one-half (D) two-fifths (E) two-thirds

2. Which number makes this number sentence true?
   □ - 5 = 9
   (A) 0 (B) 4 (C) 12 (D) 9 (E) 14

3. What is the perimeter of the quadrilateral shown?
   (A) 13 cm (B) 15 cm (C) 17 cm (D) 19 cm (E) 21 cm

4. Which of the following decimal numbers has the smallest value?
   (A) 0.0002 (B) 0.002 (C) 0.02 (D) 0.2 (E) 2.0

5. (\frac{1}{2} + \frac{2}{4} - \frac{4}{8}) =
   (A) (\frac{1}{2}) (B) 1 (C) (1\frac{1}{2}) (D) 2 (E) 4

6. Suri has a number of 20-cent and 50-cent coins. Which of the following amounts of money is it NOT possible for her to make?
   (A) 50 cents (B) 60 cents (C) 80 cents (D) 30 cents (E) 70 cents

真题文字详解(英文)

40 2021 AMC Upper Primary Solutions

Upper Primary Solutions

1. (Also MP3) There are 3 equal parts and 2 are green, so ( \frac{2}{3} ) is green, hence (E).

2. (Also MP7) The unknown number is 5 more than 9, which is 14, hence (E).

3. The perimeter is (4 + 4 + 4 + 9 = 21) centimetres, hence (E).

4. Writing as fractions, the numbers in (A)-(E) are ( \frac{2}{10000}, \frac{2}{1000}, \frac{2}{100}, \frac{2}{10}, \frac{2}{1} ), and the smallest is the one with the largest denominator. This is ( \frac{2}{10000} ), hence (A).

5. ( \frac{1}{2} + \frac{2}{4} - \frac{4}{8} = \frac{1}{2} + \frac{1}{2} - \frac{1}{2} = \frac{1}{2} ), hence (A).

6. Suri cannot make 30 cents. She cannot use a 50c coin since this is already too much. So she must only use 20c coins, but then she can only make multiples of 20 cents. All of the other amounts are possible: 50 cents from one 50c coin, 60 cents from three 20c coins, 80 cents from four 20c coins and 70 cents from one of each coin, hence (D).

7. After cutting, the sheet of paper will be made from a number of panels each of which is a long rectangle with a curved top as shown. Only (A) is made of these panels, hence (A).

8. (Also MP11) There are 4 students ahead of him, 8 behind him, and Leo himself. So there are (4+1+8=13) students in line, hence (E).

9. Thyme and fennel are equal, so thyme also weighs 5 grams. Sage weighs as much as fennel and thyme combined, which is 10 grams. Mint weighs as much as fennel, thyme and sage combined, which is 20 grams, hence (D).