Re: [計量] 麻煩各位 ^^
※ 引述《collings0628 (collings)》之銘言：
: How many two-digit positive integers N have the peoperty that the sum of N and
: the number obtained by reversing the order of the digits of N is a perfect
: square? (A)4 (B)5 (C)6 (D)7 (E)8 Ans:E
設 N = 10x + y ； x 及 y 各為 0-9 之間的整數
(10x + y) + (10y + x) = 11x + 11y = 11 (x + y) 為某整數的平方
=> x 2 3 4 5 6 7 8 9
y 9 8 7 6 5 4 3 2
共8組解
: Eight light bulbs numbered 1 through 8 are arranged in a circle. The bulbs are
: wired so that every third bulb, counting in a clockwise direction, flashes
: until all bulbs have flashed once. If the bulb numbered 1 flashes first,
: which numbered bulb will flashed last? (A)2 (B)3 (C)4 (D)6 (E)7 Ans:D
亮的順序 1,4,7,2,5,8,3,6
最後亮的是 6
: If y不等於3 and 3x/y is a prime integer greater than 2, which of the following
: must be ture?
: I. x=y
: II. y=1
: III. x and y are prime integers.
: Ans: None
若該質數為3 => x=y 即符合條件
故 II、III 不對
若該質數a不為3 => x=(y/3)*a
故 I 不對
: In the xy-plane, if the equation of the line K is ax^2 + bx + c =0, which of
: the following must be ture?
: I. If a is postive, the x-intercept is postive.
: II. If b is postive, the slop is postive.
: III. If a and b are negative, the slop is negative.
: Ans: III only 為什麼I不行@@
: 比大小
: 條件: The sum of seven integers is -1.
: Column A: The maximum number of the seven integers that can be large than 13
: Column B: 6
: Ans:C 不知是不是我會錯意,求不出C這答案
: A bus trip of 450 miles would have taken 1 hour less if the average speed S of
: the trip had been greater by 5 miles per hour.
: Column A: The average speed S, in miles per hour, for the trip
: Column B: 50
: Ans: B 題目給的條件似乎怪怪的?
450/S = 450/(S+5) + 1
化簡 => S^2 + 5S - 2250 = 0
=> (S+50)*(S-45) = 0
=> S = -50 或 45
但 S 不為負數 因此 S = 45 < 50
選B
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06/01 09:41, , 1F
06/01 09:41, 1F
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