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第 71 樓 / voice
- 時間: 2012-11-21 09:04
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- 時間: 2012-11-21 09:16
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- 時間: 2012-11-21 09:19
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- 時間: 2012-11-21 09:21
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- 時間: 2012-11-21 17:09
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- 時間: 2012-11-22 09:48
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- 時間: 2012-11-22 22:55www.cemc.uwaterloo.ca/...ontest.pdf
第16題:
A 51 cm rod is built from 5 cm rods and 2 cm rods. All of the 5 cm rods must come fi rst, and are followed by the 2 cm rods. For example, the rod could be made from seven 5 cm rods followed by eight 2 cm rods. How many ways are there to build the 51 cm rod?
(A) 5 (B) 6 (C) 7 (D) 8 (E) 9
兒子抱怨沒有答案,他說因為題目是All of the 5 cm rods,用了 rods 所以不可以是 一個 5cm 的rod 在前面。 所以 只能有 4種 辦法。
@NEXT
@voice -
- 時間: 2012-11-22 23:28
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- 時間: 2012-11-23 08:55
zyoyl 寫道:www.cemc.uwaterloo.ca/...ontest.pdf
第16題:
A 51 cm rod is built from 5 cm rods and 2 cm rods. All of the 5 cm rods must come fi rst, and are followed by the 2 cm rods. For example, the rod could be made from seven 5 cm rods followed by eight 2 cm rods. How many ways are there to build the 51 cm rod?
(A) 5 (B) 6 (C) 7 (D) 8 (E) 9
兒子抱怨沒有答案,他說因為題目是All of the 5 cm rods,用了 rods 所以不可以是 一個 5cm 的rod 在前面。 所以 只能有 4種 辦法。
@NEXT
@voice
我還真見過題目的名詞是復數排除單數在外的答案。 不過這裡的競賽題不會這麼陰險, 出現有歧義的答案。 比如這道題, 答案就是從5開始, 有5就不會有4。 有4就不會有5。 按要求找出正確答案即可, 也不能太鑽牛角尖。 做題不單要算出答案, 還要看出題人的想法, 所以對答案的設置也是很藝術的。
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- 時間: 2012-11-24 23:18
If your kids are good at Math
