2022 ACJC P1 Q9

2022 ACJC P1 Q9

10 marks
Prelims
  1. Mr Chan’s monthly pay for the first quarter of the year (i.e. first three months) is \(\$3000\). For the second quarter monthly pay, he gets an increment of \(60\%\) of his first quarter monthly pay. Subsequently, from the third quarter onwards, he gets an increment of \(60\%\) of his previous increment every quarter.
    \({{Q}_{n}}\) denotes his monthly pay for the \({{n}^{\mathrm{th}}}\) quarter, where \(n\ge 1\).
    1. Prove that \({{Q}_{n}}=7500\left( 1-{{0.6}^{n}} \right)\).[3]
    2. Find to the nearest dollar, his pay for his \(17\mathrm{th}\) month of work.[1]
    3. Find to the nearest dollar, his total salary for the first two years of work.[2]
    4. Mr Chan decides to quit his job when his increment is less that \(\$80\). How many months will he stay in this job?[1]
  2. Mr Chan’s company is planning to implement a loyalty incentive scheme to retain workers with relevant skills and experience. \(10\) chosen workers will receive a loyalty incentive of \(\$90\) in their pay every month. This monthly loyalty incentive will increase by \(\$40\) every year. The company sets aside a budget of \(\$200\,000\) for this scheme.
    1. what is the maximum number of years for which this scheme can be implemented with this budget?[2]
    2. what is the highest loyalty incentive amount Mr Chan can hope to receive if he is selected for this scheme?[1]

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Answer:(a)(i) \(Q_n=7500(1-0.6^n)\) (ii) \(\text{SGD}\hspace{0.5em}7150\) (iii) \(\text{SGD}\hspace{0.5em}146817\) (iv) \(24\) months (b)(i) \(7\) years (ii) \(\text{SGD}\hspace{0.5em}330\) in the seventh year

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