马上要考了 急！几道prep数学

lmf0801

马上要考了 急！几道prep数学
1  The numbers 75 can be  written as the sum of  the squares of 3 different positive intergers  What is the sum of these 3 intergers
17  16   15 14  13

2 Inx-yplane at what two points does graph of y=(x+a)(x-a)intersects the x-axis?
(1)  a+b=-1   (2)  the graph intersects the  y-axis  (0-6)

3 A certain library assess fines for overdue books as follow on the frist day that a book is overdue The total fine is 0.1$.For each addtional day  that a book is overdue the total fine is either increased by 0.3 or doubled whichever result  in the lesser amount that is the total fine for a book on forth day it is overdue
0.6            0.7              0.8              0.9            1.0
这道题我想问一下这个doubled 难道不是在上一次的本金+fine上进行doubled 的吗  难道只是按第一次的fine 0.1 doubled的吗
然后后面都是这个fine在相加？？？


4    Six countries in a certain region sent a total of 75represetive to an international congress . and no two counteries sent  the same numbers of representives of the six countries . if country A  sent the second  greatest numbers of representives did country A sent at least 10 representives?
(1)  One of six counteries sent 41 representives to congress
(2)  Country A sent fewer than 12 representives to congress


5    Hery purchase   3 items during a sale  he received a 20 present discount off the regular price of  the most expensive items and a 10 persent discount  off the regular price of each  of the  other items  was the toal amount of  the 3 discounts greater than 15 precent of the sum of the regular price of  the 3 items ?
(1)The regular price of the most expensive item was $50 and the regular of the next expensive item was $20
(2) the rugular price of the least expensive items was $15
求助这道题的翻译 ！！

lmf0801

up

phenicia

第一题： 1+5+7=13， 1+25+49=75

lmf0801

第一题： 1+5+7=13， 1+25+49=75

-- by 会员 phenicia (2010/8/21 17:19:08)

是凑出来的吗？ 还是怎么推出这3个数的？？

yougushizi

马上要考了 急！几道prep数学
1  The numbers 75 can be  written as the sum of  the squares of 3 different positive intergers  What is the sum of these 3 intergers
17  16   15 14  13

这题选13
1，5，7

2 Inx-yplane at what two points does graph of y=(x+a)(x-a)intersects the x-axis?
(1)  a+b=-1   (2)  the graph intersects the  y-axis  (0-6)
这题选B
a^2=6,交点是正负根号6
(1)里面b莫名其妙的。

3 A certain library assess fines for overdue books as follow on the frist day that a book is overdue The total fine is 0.1$.For each addtional day  that a book is overdue the total fine is either increased by 0.3 or doubled whichever result  in the lesser amount that is the total fine for a book on forth day it is overdue
0.6            0.7              0.8              0.9            1.0
这道题我想问一下这个doubled 难道不是在上一次的本金+fine上进行doubled 的吗  难道只是按第一次的fine 0.1 doubled的吗
然后后面都是这个fine在相加？？？
这题选B，第一天0.1，第二天0.2（放弃0.4），第三天0.4（放弃0.5），第四天0.7（放弃0.8）


4    Six countries in a certain region sent a total of 75represetive to an international congress . and no two counteries sent  the same numbers of representives of the six countries . if country A  sent the second  greatest numbers of representives did country A sent at least 10 representives?
(1)  One of six counteries sent 41 representives to congress
(2)  Country A sent fewer than 12 representives to congress
这题选E
比如说9，8，7，6，4
和11，8，7，6，2
都行

5    Hery purchase   3 items during a sale  he received a 20 present discount off the regular price of  the most expensive items and a 10 persent discount  off the regular price of each  of the  other items  was the toal amount of  the 3 discounts greater than 15 precent of the sum of the regular price of  the 3 items ?
(1)The regular price of the most expensive item was $50 and the regular of the next expensive item was $20
(2) the rugular price of the least expensive items was $15
求助这道题的翻译 ！！
这题选C
意思是H买了3个东，最贵的东打了8折，剩下两个打了9折。问总的折扣是不是比三个东全都打八五折打的多。
0.2x+0.1y+0.1z>0.15(x+y+z)
就是问，x>y+z?
A给了x,y,B给了z

-- by 会员 lmf0801 (2010/8/21 11:24:26)

derek22604

第一题：
因为是三个数平方相加得75，所以，判定3个数字范围在1-7之间（3个数字最大不能大于8，如果是8找不到另外两个数字，同是，至少有一个数字大于5）；
1-7的平方，尾数可能性为1，4，5，6，9，要得到尾数为5，只有两种可能：1，5，9或者4，6，9；
然后4，6，9排除，1，5，9的情况就是1，5，7。

不过这么做完我觉得还不如直接凑来得快…

derek22604

马上要考了 急！几道prep数学
1  The numbers 75 can be  written as the sum of  the squares of 3 different positive intergers  What is the sum of these 3 intergers
17  16   15 14  13

这题选13
1，5，7

2 Inx-yplane at what two points does graph of y=(x+a)(x-a)intersects the x-axis?
(1)  a+b=-1   (2)  the graph intersects the  y-axis  (0-6)
这题选B
a^2=6,交点是正负根号6
(1)里面b莫名其妙的。

3 A certain library assess fines for overdue books as follow on the frist day that a book is overdue The total fine is 0.1$.For each addtional day  that a book is overdue the total fine is either increased by 0.3 or doubled whichever result  in the lesser amount that is the total fine for a book on forth day it is overdue
0.6            0.7              0.8              0.9            1.0
这道题我想问一下这个doubled 难道不是在上一次的本金+fine上进行doubled 的吗  难道只是按第一次的fine 0.1 doubled的吗
然后后面都是这个fine在相加？？？
这题选B，第一天0.1，第二天0.2（放弃0.4），第三天0.4（放弃0.5），第四天0.7（放弃0.8）


4    Six countries in a certain region sent a total of 75represetive to an international congress . and no two counteries sent  the same numbers of representives of the six countries . if country A  sent the second  greatest numbers of representives did country A sent at least 10 representives?
(1)  One of six counteries sent 41 representives to congress
(2)  Country A sent fewer than 12 representives to congress
这题选E
比如说9，8，7，6，4
和11，8，7，6，2
都行

5    Hery purchase   3 items during a sale  he received a 20 present discount off the regular price of  the most expensive items and a 10 persent discount  off the regular price of each  of the  other items  was the toal amount of  the 3 discounts greater than 15 precent of the sum of the regular price of  the 3 items ?
(1)The regular price of the most expensive item was $50 and the regular of the next expensive item was $20
(2) the rugular price of the least expensive items was $15
求助这道题的翻译 ！！
这题选C
意思是H买了3个东，最贵的东打了2折，剩下两个打了1折。问总的折扣是不是比三个东全都打一五折大的多。
0.2x+0.1y+0.1z>0.15(x+y+z)
就是问，x>y+z?
A给了x,y,B给了z

-- by 会员 lmf0801 (2010/8/21 11:24:26)

-- by 会员 yougushizi (2010/8/21 17:29:59)

最后一题应该是A吧。
因为最贵的是50，第二贵的是20，也就是说剩下那个肯定小于20，所以x必定大于y+z

daisyyulan

第三题感觉应该是0.8？
第一天0.1，第二天0.2（放弃0.4），第三天0.4（放弃0.7），第四天0.8（放弃1.0）

daisyyulan

20% off应该是指打了8折

yougushizi

For each addtional day  that a book is overdue the total fine is either increased by 0.3 or doubled whichever result  in the lesser amount that is the total fine for a book
我感觉是每天都作为一个新的起点来判断第三天有两个选择，0.2+0.3或者0.2*2=0.4，因此我觉得是放弃0.5，不是放弃0.7，同理第四天在0.8和0.7之间选，放弃0.8.
不知道是不是我理解有误，大家来帮个忙？

第三题感觉应该是0.8？
第一天0.1，第二天0.2（放弃0.4），第三天0.4（放弃0.7），第四天0.8（放弃1.0）

-- by 会员 daisyyulan (2010/8/21 19:16:22)