(1) w > 2
(2) z < 2 A:A(為何選A?)
請問在類似的題目中,是否應考慮到w,z為integer?
2.A company has assigned a distinct 3-digit code number to each of its 330 employees. Each code number was formed from the digits
2, 3, 4, 5, 6, 7, 8, 9
and no digit appears more than once in any one code number. How many unassigned code numbers are there?A:6(請問如何解阿?)
3.If the sequence x1 , x2, x3, …, xn, … is such that x1 = 3 and xn +1 = 2xn – 1 for n = 1, then x20 –
x19 =?A: 219
(完全沒思路><)
4.The average (arithmetic mean) of the 5 positive integers k, m, r, s, and t is 16, and k < m
< r < s < t. If t is 40, what is the greatest possible value of the median of the 5 integers?A:18(想不出來)
5.Three printing presses, R, S, and T, working together at their respective constant rates, can do a certain printing job in 4 hours. S and T, working together at their respective
constant rates, can do the same job in 5 hours. How many hours would it take R, working alone at its constant rate, to do the same job?A:20(沒思緒><)
1.根据条件1W大于2那么题目的等式2边除以W则z<2/w;2/w是可以得出小于1的,是题目要的结果。
2 p(8,3)=336用去330还剩下6个
3我的做法是先算出前4个项(3,5,9,17),看个规律,得出通相1+2^n这样可以算出结果了。
4,根据题目可以得前4个数字得和是40,要中数最大,那么K,M要尽量得小,这样才会使平均值为10,所以k,m分别为1,2,那么R,S得和是37,又S大于R,而且S要尽量得小才可以使R取得最大。
5设他们分别得速度使R S T,那么4(S+T+R)=1;5(S+T)=1根据2个方程可以解得,R为1/20那么R单独要20小时了。
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