有鑑於上集的內容似乎嚇怕了不少小卒會員(從回覆的數目就可見一斑了

),所以今集將集中火力討論69年的Paper 1和2,至於Paper 3,則會蜻蜓點水地看看一些「有趣」

的題目。
(寫作時才發現,原來AMaths「開科」初期,變化很大,是故上集一連氣講兩年的承諾,因為字數關係,實在受不了---考試中,26/6考Pure……為免令大家失望,都係分兩集講吧,希望大家見諒。

)
69年的Paper 1,第一題都幾令人怕怕的。
1969 I 1. Assuming that 1.4 + 2.5 + … + n(n + 3) is equal to (n/3)(n + 1)(n + 5) for a given value of n, obtain a
similar expression for 1.4 + 2.5 + … + n(n + 3) + (n + 1)(n + 4). (3 marks)
是否一道MI的題目?
新數的「侵襲」

,使AMaths繼續出現Probability。
1969 I 5. How many numbers between 4000 and 7000 can be formed by using 3, 4, 5, 6 as digits, so that any digit
may be repeated? (4 marks)
1969 I 6. Find the chance of throwing a total of 5 in one throw with 2 dice. (4 marks)
兩道題目,都是現在的Maths Paper II Section B的形式,不過應該會淺易一點,以免令本身已經令噴血

的考生人數激增。
看過短題目了,觀賞一下長題目吧。
有別於68年,69、70年長題目的選題方面又再rearrange過。
在Paper 1方面,是在兩個Group中選三題,每個Group有三題,最多只可選兩題。至於Paper 2,則改為六選三。Paper 3則改為兩個Group,每Group四題,最多只可選兩題。
Paper 1 Group I的第一題,乃為一道現今Maths的variation題目,是挺淺易的。
1969 I 12. Certain articles, each costing $10 to manufacture, are put on the market. The number sold per annum
varies inversely as the square of the unit selling price. When the unit selling price is $25, 6400 articles are sold.
Find the number of articles that must be sold, and their unit selling price, to give the maximum annual profit.
突然竟在Paper 1見到Mechanics的題目??!!
1969 I 14. Initially a particle moves with a velocity of 24 ft/sec along a straight line and its acceleration after t seconds
is (8 - 15t^2) ft/sec^2. Given that it stops instantaneously and reverses its direction of motion only once,
show that this takes place when t = 2.
Calculate (a) the distance travelled in the first 2 seconds, and
(b) the total distance travelled in the first 4 seconds.
可以把它看作Physics題,但出卷想考核的,是微積分的應用。可是,從現今的學生角度看,卻只會聯想起開初修Physics Mechanics時的「奪命四式」。
Group II第1題,是1道MI加Binomial的題目。
1969 I 15. (a) Prove by mathematical induction that if n is a positive integer, f(n) = 3^2n - 1 is divisible by 8.
(Hint: consider f(n + 1) - f(n).)
(b) Obtain the binomial expansion of (x + 2y)^6 and use it to calculate 1.02^6, correct to six places of decimals.
兩道風牛不相馬及的題目,綜合在一道長題目了。
Paper 2的短題目,大部分都是CoGeo和微積分的題目,再湊合一些簡易的algebra如rationialize和G.S.。
長題目,第一題是玩玩地球表面,考的是Trigo的應用。
1969 II 10. The dotted line in the above figure represents the surface of the earth. E is the eye-level of an observer
stationed at a height h feet above the point A on the surface.
(a) This observer can just see a pont T on the earth's surface, distant 's' miles from E. Prove that the
realtionship's is approximately equal to (1.5h)^1/2' is true.
(Take 1 mile = 5280 feet and assume the earth is a spher of radius 4000 miles)
(b) For values of h between 0 and 100, plot a graph showing the relationship between h and s.
(c) From your graph estimate whether a man floating in calm water can be seen by an observer
(i) 15 miles away on the top of a 100-foot cliff,
(ii) at a point 50 feet high on a ship 8 mile away.
(d) What is the greatest distance, to the nearest mile, the observer 50-feet high on the ship can see the
other observer on the 100-foot cliff?
(Neglect the heights of the observers.)
(c) part的「IQ問題」,真的可以考起不少考生的,而且錯就是錯,沒有灰色地帶的。前提是,(b) part的graph不能plot錯。
概念不深,但挺煩的題目。
接著的11和12題,在悶蛋的純Trigo代數和Binomial應用題,不多詳述。
13題,Physics再現!
那是一道光從空氣進入水的速度題,考的卻是Trigo。換句話說,就是披著Refraction的外衣,實質是三角學的應用題。
跳至15題,神奇三點再現。
1969 I 15. The triangle ABC has vertices at the points A(1,3), B(0,0) and C(5,0).
(a) Calculate the coordinates of
(i) the centroid G (where the medians intersect)
(ii) the orthocentre H (where the altitude intersect)
(iii) the circumcentre O (the cnetre of the circumscribed circle).
(b) Prove that O, G, H lie on the same straight line and that GH = 2OG.
一道今天Maths考生應該懂得答,但煩得令人七竅生煙的題目。
Paper 3,此年考的,多了一點take moment的題目,lamina繼續出現,CE Physics經典的「斜板題」亦粉墨登場。
第4題至第10題的短題目,為免考生因為複雜的概念弄得做不完,容許他們用不寫詳細解釋,簡略地講出答案就可以了。
「For Questions 4-10, detailed explanation is not required.」
那麼,第1至3題是甚麼東東呢?
是AMaths前無古卷(其實都是得兩年......

),後應該都沒有來考的題目---符號和是非題。
先看有趣的instruction。
「For Questions 1-3, no explanation is required, and no working need to be shown, but there should be no guess work.」
在給這個instruction時,考生是不會因為錯的答案而被扣分的。(在試卷上沒有提及任何扣分的字眼)
第1題,是分辨scalar和vector的題目。
當中有八個quantity要考生去分辨:Acceleration、Force、Kinetic energy、Length、Mass、Mass x velocity、Time與及Horse power。
第2題,是一道v-t graph的題目,考生要在圖中辨別出四句statements的對錯。
第三題,是給了一幅,然後讓考生比較圖中兩件物件(P、Q)的PE、speed、acceleration和time taken的大小,用符號表達。
可見,69年的Paper 3,可謂饒有特色的。
同時,因為太屈的關係,這類符號和是非題在70年沒有再出現了。
下次將帶大家邁向七十年代,風眼之處。