今天我们给出第三组袋鼠竞赛的题目（每个年级组一道题），并给出第二组题目（见《袋鼠数学竞赛题选（二）》）的解答。

1-2年级组

A ship was attacked by pirates. One by one they were climbing a rope to get to the ship. The pirate captain was in the middle and he was also the eighth one from the beginning. How many pirates were on the rope?

一艘船被海盗袭击了。海盗们一个接一个地沿着一条绳子攀爬到船上。海盗首领的位置在正中间，他是第8个爬上船的。共有多少个海盗沿着这条绳子爬上船？

3-4年级组

There are 5 ladybugs (see fig.). Two ladybugs are friends with each other if the numbers of spots that they have differ exactly by 1. On Kangaroo Day each of the ladybugs sent to each of her friends one SMS greeting. How many SMS greetings were sent?

有5只瓢虫（见图）。如果两只瓢虫背上的黑点数量刚好相差1，那么它们就是朋友。在袋鼠日那天，每只瓢虫都给它的朋友发了一条祝福短信。它们一共发了多少条短信？

5-6年级组

Lucy and her mother were both born in January. Today, March 19 2015, Lucy adds the year of her birth, the year of her mother's birth, her age, and her mother's age. What result does she get?

Lucy和她妈妈都是在一月份出生的。今天是2015年3月19日，Lucy把她自己的出生年份、她妈妈的出生年份、她自己的岁数和她妈妈的岁数都加在一起。请问计算结果是多少？

7-8年级组

A square with area 30 is divided in two by a diagonal and then into triangles, as shown. The areas of some of these triangles are given in the diagram. Which part of the diagonal is the longest?

如下图，一个正方形的面积是30平方厘米，被它的一条对角线分成两个三角形，每个三角形又被分成更小的三角形。其中一些三角形的面积已经在图中标示出来了。对角线的哪个小段长度最长？

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下面是第二组题目的参考答案和解析。

1-2年级组

Place each of the numbers 1, 2, 3, 4, 5 into one box so that everything is correct. Which number goes into the box marked with question mark?

把数字1，2，3，4，5分别填入下图中的方框内，使得其中的算式都成立。标注问号的方框内应该填哪个数字？

【答案：E】标注了问号的方框里的数是最上方的两个数的和，同时也是它右方和最下方的两个数之和。所以方框里的数应该是所有数里面最大的。

3-4年级组

Josip has 4 toys - a car, a doll, a ball and a ship. He wants to put them on a line on a shelf. The ship has to be next to the car and the doll has to be next to the car. In how many ways can he arrange them so that all the conditions are fulfilled?

Josip有四个玩具：一辆车，一个洋娃娃，一个球和一只船。他想把这些玩具在架子上排成一排。船要跟车紧挨着，洋娃娃也要跟车紧挨着。他有多少种不同的方式排列这些玩具？

5-6年级组

On Jump Street, there are 9 houses in a row. At least one person lives in each house. Any two neighbouring houses together are inhabited by at most six people. What is the largest number of people that could be living on Jump Street?

有9栋房子依次座落在Jump街上。每栋房子里至少住了一个人，而且任意两栋相邻的房子里住的人数不超过6人。Jump街上最多住了多少人？

7-8年级组

A bush has 10 branches. Each branch has either 5 leaves only or 2 leaves and 1 flower. Which of the following could be the total number of leaves the bush has?

一丛灌木有10个分枝。每个分枝上要么有5片叶子，要么有2片叶子和1朵花。这丛灌木的叶子数量可能是多少？

【答案：E】称有5片叶子的分枝为第一类分枝，有2片叶子和1朵花的分枝为第二类分枝。如果10个分枝都是第一类分枝，则共有50片叶子。把一个第一类分枝换成第二类分枝，叶子就减少3片。所以，50和最终的叶子数量之差必定是3的倍数，或者说，最终的叶子数量和50关于3同余。50除以3的余数为2，而选项A~D的数除以3的余数都不是2。