用英语出的小升初奥数题（有翻译和答案）

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 3、The number of diagonals that can be drawn in a regular polygon with twenty sides (icosagon) is_____. 4、If a and b are integers, 10Ä3=1,152Ä7=3, and then 379Ä6 is equal to_____. 5、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____. 6、The greatest number of Mondays which can occur in 45 consecutive days is____ 7、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____. 8、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) 9、The areas of the faces of a rectangulabox are 84 cm2 , 70 cm2and 30 cm2.The volume of the box in cm3 is____. 10、 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] 答案：1，十进制用0～9表示所有数，二进制只用0和1表示 下面哪个数在八进制下是非法的？ A)128（八进制用0～7） 3，一个二十边形内可画出多少条对角线？ 170条（20选2，减去20条边） 4，如果a和b都是整数，10Ä3=1,152Ä7=3, 那么 379Ä6等于？ 题目似乎有点问题，看不懂 5、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____. 5，两个数的比例为2:3，如果分别给两个数加4，则他们的比例变为5:7。 原来的两个数的和为？ 40（16和24） 6、The greatest number of Mondays which can occur in 45 consecutive days is____ 6，连续45天最多能出现多少个星期一？ 6个 7、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，Saul在玩一个电视游戏，击中得4分，没击中扣6分。20个回合之后他得了30分，那么他有多少次没击中？ 5次（4×15-6×5=30） 8、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，A,B和C三个女孩进行百米短跑比赛。A跑完的时候，B在A背后10米；B跑完的时候，C在B背后20米。那么A跑完的时候，C在A后面多少米？（假设他们一直匀速跑） 28米。（B的速度是A的90%，C是B的80%，C是A的72%） 9、The areas of the faces of a rectangulabox are 84 cm2 , 70 cm2and 30 cm2.The volume of the box in cm3 is____. 一个长方体盒子的三个面面积是84cm2,70cm2和30cm2。这盒子的体积是多少？ 420cm3（14cm×6cm×5cm） 10、 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] 你有1kg，3kg和9kg3个砝码和一个天平，你可以称出多少个不同的重量？（记住砝码可以放在天边两边的任意一边） 13个(1～13kg)