Question 11
- It takes 8 students two – thirds of an hour to fill 12 tanks with water. How many tanks of water will 4 students fill in one – third of an hour at the same rate?
- A chord, 20 cm long, is 12 cm from the centre of the circle. Calculate, correct to one decimal place, the:
(i) angle subtended by the chord at the centre of the circle;
(ii) perimeter of the minor segment cut off by the chord. [Take 
].
Observation
The Chief Examiner reported that majority of the Candidates’ that attempted this question did very well but a few still had issues with Rates and Proportion, hence, the performance in part (b) was better than part (a).
In part (a) Candidates’ were expected to convert two-thirds of an hour to minutes which is 40 minutes and one-third of an hour to minutes which is also 20 minutes. If it takes 8 students 40 minutes to fill 12 tanks, then it will take 1 student (8 
40) minutes to fill the tanks. Therefore, 4 students will take 
= 80 minutes. Then 80 minutes spent to fill 12 tanks. At 1 minute, then 
tanks will be filled. Therefore, at 20 minutes, 
= 3 tanks will be filled.
In part (b), the Candidates’ responded as follows:
Let 
be the angle between the radius and length of the chord from the centre. Then, 
. Therefore, angle subtended by the chord at the centre of the circle is 2 
39.8o = 79.60 (Correct to 1 decimal place).
Also, in part (b) (ii), the perimeter of the minor segment is 
, where 
= 15.62 cm.