2009 袋鼠数学 C-Benjamin 真题 答案 详解

英文真题

International Kangaroo Mathematics Contest 2009 - Benjamin
Benjamin Level: class (5 & 6) Max Time: 2 Hours

3-Point Problems

1. Among these numbers, which is even?
   (A) 2009
   (B) 2 + 0 + 0 + 9
   (C) 200 - 9
   (D) 200 × 9

2. Where is the smiley?
   (A) In the circle and the triangle, but not the square.
   (B) In the circle and the square, but not the triangle.
   (C) In the triangle and the square, but not the circle.
   (D) In the circle, but not in the square or the triangle

3. The smallest number of digits to be erased in the number 12323314 in order to get a number that reads identically from left to right and from right to left, is equal to
   (A) 1
   (B) 2
   (C) 3
   (D) 4

4. There are three boxes: white, red and green. One of them contains a bar of chocolate, the second contains an apple, and the third is empty. Find the chocolate, if it is known, that the chocolate is either in the white or in the red box, and the apple is neither in the white nor in the green box.
   (A) white
   (B) red
   (C) green
   (D) impossible to determine

5. A bridge is built across the river. The river is 120 meters wide. One quarter of the bridge is over the left river bank and one quarter of the bridge is over the right river bank. How long is the bridge?
   (A) 150 m
   (B) 180 m
   (C) 210 m
   (D) 240 m

6. There are squares of three different sizes at the picture. The side of the smallest one is 20 cm long. What is the length of the marked bent line?
   (A) 380 cm
   (B) 400 cm
   (C) 420 cm
   (D) 440 cm

7. There are cats and dogs in the room. The number of cats' paws is twice the number of dogs' noses. Then the number of cats is
   (A) twice the number of dogs
   (B) equal to the number of dogs
   (C) half the number of dogs
   (D) (\frac{1}{4}) of the number of dogs