Observation

The Chief Examiner reported that this question was attempted by majority of the candidates and they performed well in it. The report further stated that candidates’ performance in part (a) was better than what it was in part (b).
In part (a), it was reported that while majority of the candidates were able to simplify the fraction correctly, a few others were unable to obtain the appropriate LCM. They were expected to obtain the LCM of the numerator as 20. Thereafter, they would simplify the numerator to obtain . Following the same procedure, they would simplify the denominator to obtain . Therefore,  now becomes  =  = 3.         
In part (b), it was reported that some candidates did not interpret the question correctly. They were expected to respond as follows:
If n = number of students in the class, then total age of students in the class = 15n years. When the age of the teacher is added, the total age now becomes (15n + 45) years and the number of people in the class = (n + 1). From the second statement, it implied that  = 18. Solving this equation gave n = 9.