2020 澳洲 AMC B-UpperPrimary 真题 答案 详解

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中英双语真题

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英文真题

Upper Primary Division
Questions 1 to 10, 3 marks each

1. How many pieces have been placed in the jigsaw puzzle so far?
   (A) 25
   (B) 27
   (C) 30
   (D) 33
   (E) 35

2. What is half of 2020?
   (A) 20
   (B) 101
   (C) 110
   (D) 1001
   (E) 1010

3. What is the perimeter of this triangle?
   (A) 33 m
   (B) 34 m
   (C) 35 m
   (D) 36 m
   (E) 37 m

4. Which fraction is the largest?
   (A) one-half
   (B) one-quarter
   (C) one-third
   (D) three-quarters
   (E) six-tenths

真题文字详解(英文)

2020 AMC Upper Primary Solutions 43

Upper Primary Solutions

1. (Also MP6) Alternative 1 The completed puzzle will have $5 \times 7 = 35$ pieces, but 5 pieces have not been placed yet, so the number of correctly placed pieces is $35 - 5 = 30$, hence (C).

Alternative 2 There are 5 rows, each with 6 correctly placed pieces, giving a total of $5 \times 6 = 30$, hence (C).

1. (Also J2) $2020 \div 2 = 1010$, hence (E).

2. (Also MP7, J3) The perimeter is the sum of the three sides: $11 + 7 + 16 = 34$ metres, hence (B).

3. Comparing to $\frac{1}{2}$, only $\frac{3}{4}$ and $\frac{6}{10}$ are larger. Of these, $\frac{3}{4} = 0.75$ and $\frac{6}{10} = 0.6$, so that $\frac{3}{4}$ is the largest, hence (D).

4. The angle $PXQ$ is an acute angle, so less than $90^\circ$. It is halfway between $40^\circ$ and $50^\circ$, which makes it $45^\circ$, hence (A).

5. Each graph shows time from left to right and height from bottom to top. The left end of the curve represents the beginning of the journey, at the lowest height. Somewhere in the middle of the curve is the highest point at the top of the hill. Lower than this is the right end of the curve, which represents the height of the lake. So the graph will be an up-then-down shape similar to that shown. Only (A) matches this, hence (A).

6. Each 1 is 10 tenths, so 6 is 60 tenths. Also 0.2 is two tenths, so that 6.2 is 62 tenths, hence (A).

7. (Also MP10) The red column (Nony) is taller than the blue column (Cera) in January, March, May and June, hence (D).