[計量] 請教幾題計量問題

看板GMAT (GMAT入學考試)作者Vucasee (Epsilon)時間15年前 (2011/04/28 23:30)推噓0(0推 0噓 0→)

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小弟遇到幾個問題，煩請大大不吝指導。題目是在GMAT 數學高分突破的數學機考模擬150題中的幾題。書中只有答案但沒有詳解。 8. The arithemetic mean of a data set is 46 and the standard deviation of the set is 4. Which value is exactly 1.5 standard deviations from the arithmetic mean of the set? (A) 42 (B) 44.5 (C) 47.5 (D) 50 (E) 52 A: E < 這種standard deviation 的題目常常會看不懂~"~> 9. For how many integers n is 2^n = n^2 ? (A) None (B) One (C) Two (D) Three (E) More than three A: C 32. A first-grade teacher use ten flash cards, number 1 through 10, to teach her students to order numbers correctly. She has students choose four flash cards randomly, then arrange the cards in ascending order. One day, She removes the cards number "2" and "4" from the deck of flash cards. On that day, how many different correct arrangements of four randomly selected cards are possible? (A) 70 (B) 210 (C) 36 (D) 840 (E) 1680 A: A 36. A square countertop has a quare tile inlay in the center, leavin an untiled strip of uniform width around the tile. If the ratio of the tiled area of the following could be the width, in inches, of the strip? I. 1 II. 3 III. 4 (A) I only (B) II only (C) I and II only (D) I and III only (E) I,II and III <看不懂題目在講什麼..> A: E 43. Jerome wrote each of the integers 1 through 20, inclusive, on a separate index card. He placed the cards in a box, then drew cards one at a time randomly from the box, without returning the cards he had already drawn to the box. In order to ensure that the sum of all the cards he drew was even, how many cards did Jerome have to draw? (A) 19 (B) 12 (C) 11 (D) 10 (E) 3 A: B <但是如果7 odd + 5 even = 還是odd 啊, 沒辦法ensure 吧？＠＠我寫A> 60. If the value of a piece of property decreases by 10 percent while the tax rate on the property increase by 10 percent, what is the effect on the taxes? (A) Taxes increase by 10 percent. (B) Taxes increase by 1 percent. (C) There is no change in taxes. (D) Taxes decrease by 1 percent. (E) Taxes decrease by 10 percent. A: D Thanks for your time and help ~ -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 59.115.232.38