Urgent Help to solve another 3 maths problems
子女教育
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Sorry, trouble everyone again.
Q1. A goat in a horizontal ground is tied to one end of 14 m long rope. The other end of the rope is attanched to a ring which is free to slide along a fixed 20 m long horizontal rail. Find the maximum possible area that the goat can graze.
Ignore the dimension of the ring and take pi to be 22/7.
The provided answer is 1204 square m, but my answer is 1176. How can I get 1204 or the answer is wrong?
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静雯 LV7
发表于 10-4-2012 17:08:53
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Q2. A theme part isssues entrance tickets bearing 5-digit serial numbers from 00000 to 99999. If any adjacent numbers in the serial numbers differ by 5 (for example 12493), customers holding such a ticket could use the ticket to reddem a free drink. Find the number of tickets that have serial numbers with this property.
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静雯 LV7
发表于 10-4-2012 17:13:15
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Q3.
P, Q, R, S and T are equally spaced on a straight rod. P----Q----R----S----T
If the rod is frist rotated 180 degree about T, then 180 degree about S and finally 180 degree about P, which point's position remains unchanged?
I don't understand why the provided answer is R. Isn't the answer wrong again?
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jjrchome LV16
发表于 10-4-2012 23:23:05
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本帖最后由 jjrchome 于 11-4-2012 00:00 编辑
Q1.
Taking account of the distance between "goat's mouth" and the knot (say 22cm), you will get 1204m2.
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jjrchome LV16
发表于 10-4-2012 23:32:52
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静雯 发表于 10-4-2012 17:13 
Q3.
P, Q, R, S and T are equally spaced on a straight rod. P----Q----R----S----T
If the rod is ...
Q3.
P----Q----R----S----T
T----S----R----Q----P
P----Q----R----S----T
T----S----R----Q----P
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jjrchome LV16
发表于 10-4-2012 23:43:16
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本帖最后由 jjrchome 于 10-4-2012 23:49 编辑
静雯 发表于 10-4-2012 17:08 
Q2. A theme part isssues entrance tickets bearing 5-digit serial numbers from 00000 to 99999. If any ...
这个是2011年Asia Pacific Mathematical Olympiad for Primary Schools第一轮竞赛的其中一道试题啊。
抄来的答案:
先求相邻2个不等于5的。
首位可取10个,第2、3、4、5位只能取9个,共10*9*9*9*9。
所以相差5的数有 100000-10*9*9*9*9=34390个
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jjrchome LV16
发表于 10-4-2012 23:51:09
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静雯 发表于 10-4-2012 17:13 
Q3.
P, Q, R, S and T are equally spaced on a straight rod. P----Q----R----S----T
If the rod is ...
中国的初一数学竞赛中也有一道类似的题:

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jjrchome LV16
发表于 10-4-2012 23:53:47
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我要开心 LV9
发表于 11-4-2012 00:01:40
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| | P | Q | R | S | T | | | | | | | | | | | T | S | R | Q | P | | | | | P | Q | R | S | T | | | T | S | R | Q | P | | | | | | | Answer is Q.
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鹏飞狮城 LV10
发表于 11-4-2012 00:02:13
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jjrchome 发表于 10-4-2012 23:23
Q1.
On the assumption that the distance between "goat's mouth" and the knot is 22cm, you will get 1 ...
这个assumption好像不是很有说服力。为什么一定是22cm,不是5cm? 有没有更好的解释? |
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