推 geniuswen:為什麼Y軸上任何點都可能是圓心? 12/11 18:30
→ Chest:假定(4,0)跟(-4,0)兩點都在圓周上，圓心只要跟此二點距離相 12/11 23:04
→ Chest:同即符合條件，故以原題的兩點位置，Y軸上任一點均符合 12/11 23:05
※ 引述《chilis (chilis)》之銘言：
: 濤濤版31套~
: Q27:
: For each landscaping job that takes more than 4 hours, a certain contractor
: charges a total of r dollars for the first 4 hours plus 0.2r dollars for each
: additional hour or fraction of an hour, where r > 100. Did a particular
: landscaping job take more than 10 hours?
: (1) The contractor charged a total of $288 for the job.
: (2) The contractor charged a total of 2.4r dollars for the job.
: ----------------------------------------------------------------------------------------------------------------------
: Answer: B
(1)不能判斷是因為原題只說r>100，沒說上限
所以288究竟是多少的r是不能肯定的
相對之下，(2)可以明確的指出是4+7小時，所以一定超過
: Q28:
: In the rectangular coordinate system, points (4, 0) and (– 4, 0) both lie on
: circle C. What is the maximum possible value of the radius of C ?
: A. 2
: B. 4
: C. 8
: D. 16
: E. There is no finite maximum value.
: ----------------------------------------------------------------------------------------------------------------------
: Answer: E
簡單的說，因為題目問的是最大半徑
而依原題，任何Y軸上的點都可能是圓心，所以沒有半徑的最大值
: Q30:
: A train traveled from station X to station Y at a constant speed of 88 feet
: per second. Is the distance that the train traveled from station X to Station
: Y greater than 40 miles? (1 mile = 5,280 feet)
: (1) It took less than 45 minutes for the train to travel from station X
: to Station Y.
: (2) It took more than 42 minutes for the train to travel from station X
: to Station Y.
: ----------------------------------------------------------------------------------------------------------------------
: Answer: B Answer: B
這一題好像是10月的機經?(小弟11/6考試的時候似乎有遇到這一題)
先計算火車跑1mile要的時間 5,280/88=60(秒)=1分
所以要跑40mile需要40分鐘
(1)的條件無法肯定Y>40，但(2)就明確的說至少要42分鐘
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