英文奥数推出之后，家长和同学们都反映非常好，说受益匪浅。因此我们推出系列二。但同时也有些问题，很多家长反映孩子觉得比较难。首先希望家长多多辅导孩子，其实奥数知识同学们是都会的，但是有些英文单词不认识，希望查字典助孩子共同提高。另外，我们只是希望那些比较优秀的同学和学有余力的同学来做，没有必要所有同学都要会做。
1、Did you know? In the decimal number system (base 10) ten different digits, 0 to 9, are used to write all the numbers. In the binary number system (base 2) two different digits are used, i.e. 0 and 1.
Which one of the following numbers is not a valid number in the
octal number system (base 8)?
A) 128 B) 127 C) 126 D) 125 E) 124
2、The number of diagonals that can be drawn in a regular polygon with
twenty sides (icosagon) is_____.
3、If a and b are integers, 10?3=1,152?7=3, and then 379?6 is equal to_____.
4、Two numbers are in the ratio 2 : 3. When 4 is added to each number the ratio changes to 5 : 7.The sum of the two original numbers is____.
5、The greatest number of Mondays which can occur in 45 consecutive
days is____
6、Saul plays a video game in which he scores 4 for a hit and lost 6 for a miss. After 20 rounds his score is 30. The number of times he has missed is____.
7、Three girls A, B and C run in a 100 m race. When A finishes, B is 10 m
behind A and when B finishes C is 20 m behind B. How far in metres was C from A when A finished?(Let’s assume all the athletes run at a constant speed)
8、The areas of the faces of a rectangulabox are 84 cm2 , 70 cm2and 30 cm2.The volume of the box in cm3 is____.
9、You have 3 weights: 1 kg, 3 kg and 9 kg as well as an equal arm balance, as shown. How many different weight objects can you weigh with these three?
[Remember the weights may be placed on either side]
参考答案：
1、A 考察我们学过的简单的进制问题，显然8进制中没有8出现
2、170 找规律，公式为n×（n-3）÷2
3、1 定义新运算，就是求379÷6的余数。
4、40，16和24
5、7
6、5
7、28米，根据距离比求出速度比，三者的速度比为1：9/10：18/25
8、420 分解质因数
9、13种