数学大家帮忙啊，快考试了
1， If N is a positive integerless than 200, and 14n/60 is an integer then n has how many different poitive prime factors?
Answer: 3
2, Before being simplified, the instructions for computing incometax in country R were to add 2 percent of one's annual income to the average (arithmetic mean) of 100 units of Country R's currency and 1 percent of one's annual income, which of the following represents the simplified formula for computing the income tax in Country R's currency, for a persom in that country whose annual income is I?
Answer: 50+ I/40
3 If xy=1, what is the value of 2(x+y) 平方/ 2( x-y)平方？
answer: 16
4. If n and m are positive integers, what is the remainder when 3的（4n+2)次幂is divided by 10?
(1) n=1 (2) m=2
Answer: B 可是着题的公式根本不牵涉到m啊
5 In xy-plane, at what two points does the graph of y =(x+a)(x+b) interesect the x-axis?
(1) a+b=-1 (2) The graph intersects the Y-axis at ( 0,-6)
6 这题不明白什么意思
Alice's take home pay last yeat was the same each month,and she saved the same fraction of her take home pay each month, The total amount of money that she had saved at the end of the yeat was 3times the amount of that portion of her monthly take home pay that she did not save. If all the money the she saved last yeat was from her take home pay, what fraction of her take home pay did she save each monthly?
Answer: 1/5
7 All of the stocks on the over-the-counter martket are designated by either a 4-letter or a 5-letter code that is creted by using the 26 letter of the alphabet. which of the following gives the maximum number of different stocks that can be designated with these codes?
Answer: 27( 26四次方）
| -- 作者：Elaine85415 -- 数学求救， 英文原题加答案，快考试了 数学大家帮忙啊，快考试了 1， If N is a positive integerless than 200, and 14n/60 is an integer then n has how many different poitive prime factors? Answer: 3 根据题目的意思，n*7/30是正数，说明n是30的倍数，那么含有因子2，3，5（30=2*3*5），因为n小于200，不可能是210（多一个因子7），200以内30的倍数都只有因子2，3，5。所以答案是3。 2, Before being simplified, the instructions for computing incometax in country R were to add 2 percent of one's annual income to the average (arithmetic mean) of 100 units of Country R's currency and 1 percent of one's annual income, which of the following represents the simplified formula for computing the income tax in Country R's currency, for a persom in that country whose annual income is I? Answer: 50+ I/40 这个就是看懂题目的意思，要计算的是2 percent of one's annual income+the average (arithmetic mean) of 100 units of Country R's currency and 1 percent of one's annual income，也就是2%*I+（100+1%*I）/2=50+I/40 3 If xy=1, what is the value of 2(x+y) 平方/ 2( x-y)平方？ answer: 16 这个题目抄错了吧，拿X=2，Y=1/2代进去都得不到结果，楼主再看下题目。 4. If n and m are positive integers, what is the remainder when 3的（4n+2)次幂is divided by 10? (1) n=1 (2) m=2 Answer: B 可是着题的公式根本不牵涉到m啊 同奇怪，再看下题目？ 5 In xy-plane, at what two points does the graph of y =(x+a)(x+b) interesect the x-axis? (1) a+b=-1 (2) The graph intersects the Y-axis at ( 0,-6) 与X轴相交等于问Y=0时，求X=多少，能求出就是有解。 Y=0时，（X+a）（X+b）=0 X=-a or -b (1) 不充分 （2）根据条件 -6=ab 也不充分 （1）（2）合起来可以算出a,b的值。 因此应该是C 6 这题不明白什么意思 Alice's take home pay last yeat was the same each month,and she saved the same fraction of her take home pay each month, The total amount of money that she had saved at the end of the yeat was 3times the amount of that portion of her monthly take home pay that she did not save. If all the money the she saved last yeat was from her take home pay, what fraction of her take home pay did she save each monthly? Answer: 1/5 这题的意思的一年节省的钱是一个月中没有节省的钱的3倍（所以省的不多）最快的方法是把答案代进去试，又快又稳。要列方程的话设每月没有省的是X，每月的收入是Y，要求的就是X/Y咯。根据条件列等式：（Y-X）*12=3X 得出X/Y=1/5 7 All of the stocks on the over-the-counter martket are designated by either a 4-letter or a 5-letter code that is creted by using the 26 letter of the alphabet. which of the following gives the maximum number of different stocks that can be designated with these codes? Answer: 27( 26四次方） 都看成五位的，每位都有26种不重复可能。四位的看成首位为缺失的可能，所以首位是26+1种可能，其他四位26。 27*26*26*26*26 |
2, Before being simplified, the instructions for computing incometax in country R were to add 2 percent of one's annual income to the average (arithmetic mean) of 100 units of Country R's currency and 1 percent of one's annual income, which of the following represents the simplified formula for computing the income tax in Country R's currency, for a persom in that country whose annual income is I?
Answer: 50+ I/40
这个就是看懂题目的意思，要计算的是2 percent of one's annual income+the average (arithmetic mean) of 100 units of Country R's currency and 1 percent of one's annual income，也就是2%*I+（100+1%*I）/2=50+I/40
这个除以2是为什么？？。谢谢ls的
average
average (arithmetic mean) of 100 units of Country R's currency and 1 percent of one's annual income
就好象100人民币+1%的人均收入的sum然后平均
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