2005 袋鼠数学 E-Junior 真题 答案 详解

英文真题

Kangaroo 2005 — Junior Max Time: 90 min Junior 3-Point-Problems 1. Helga lives with her father, mother, brother, one dog, two cats, two parrots and four fish. How many legs do they have altogether? (A) 22 (B) 28 (C) 24 (D) 32 (E) 13 2. Sally had the fiftieth best result, and at the same time the fiftieth poorest result, at the latest Kangaroo contest in her school. How many pupils took part in the competition? (A) 50 (B) 75 (C) 99 (D) 100 (E) 101 3. There are eight kangaroos in the cells of the table (see the figure on the right). Any kangaroo can jump into any free cell. Find the least number of kangaroos which have to jump into another cell so that exactly two kangaroos remain in any row and in any column of the table. (A) 0 (B) 1 (C) 2 (D) 3 (E) 4 4. 18 pupils are crossing a road in pairs. The pairs are labeled from 1 to 9. A pair with an even label consists of a boy and a girl, and a pair with an odd label consists of two boys. How many boys are crossing the road? (A) 10 (B) 12 (C) 14 (D) 11 (E) 18 5. Johnny inflates 8 balloons every three minutes. How many balloons will be inflated after two hours, if every tenth balloon pops immediately after having been inflated? (A) 160 (B) 216 (C) 240 (D) 288 (E) 320 6. In the diagram, the five circles have the same radius and touch as shown. The small square joins the centres of the four outer circles. The ratio of the area of the shaded part of the five circles to the area of the unshaded parts of the five circles is (A) 1 : 3 (B) 1 : 4 (C) 2 : 5 (D) 2 : 3 (E) 5 : 4