SCSA Mathematics Applications Growth and decay in sequences

5 sample questions with marking guides and sample answers · Avg. score: 57.4%

Q9
2024
QCAA
Paper 1
1 mark
Q9
1 mark

Determine the 4th term for the geometric sequence that begins 1000, -900, ...

A

729

B

700

C

-700

D

-729

Q9
2023
QCAA
Paper 1
1 mark
Q9
1 mark

Determine the 6th term of the arithmetic sequence that begins 3, 9, …

A

21

B

33

C

45

D

729

Q1
2025
SCSA
Paper 1
10 marks
Q1

When people become ill, their body responds with a change to their white blood cell count (WBCC) measured in '000s cells per microlitre (cells/μL).

The table below shows a person's white blood cell count after contracting an illness.
Let nn represent the number of hours after contracting an illness.

Time (nn hours)123456
WBCC '000s (cells/μL)8.48.79   
Q1e

After an illness is diagnosed, a person receives the appropriate medication to aid their recovery. An indirect effect of the medication will be an overall reduction in the person's white blood cell count.

A person becomes ill and is given medication. Their white blood cell count ('000s cells/μL) follows the recursive rule Tm=0.5Tm1+20,T0=20T_m = -0.5T_{m-1} + 20, \quad T_0 = 20, where mm is the number of hours after the person is given the medication.

Q1a
1 mark

The person's white blood cell count is increasing at a constant rate each hour. Show that this rate is 300 cells/μL.

Q1b
1 mark

Complete the table above.

Q1c
2 marks

Determine a simplified rule for the nthn^{\text{th}} term to model the person's white blood cell count after contracting an illness.

Q1d
2 marks

Determine the white blood cell count in the person's body after 12 hours, if the white blood cell count maintains the same rate of increase.

Q1e (i)
2 marks

Determine the white blood cell count in this person at the end of the second hour.

Q1e (ii)
2 marks

Determine if the given medication, in the long run, can ensure this person's white blood cell count does not fall below 13 000 cells per microlitre.

Q6
2025
SCSA
Paper 2
13 marks
Q6

Josh lives in Sydney and Simon lives in Perth. They each decide to drive to Alice Springs to meet before driving together to Darwin. Simon and Josh will both leave for Alice Springs on Saturday, 2 January.

Due to traffic in Sydney, Josh can only drive 250 km on the first day. After this he plans to drive 3 km more each day than the previous day.

Let nn represent the number of days spent driving.

Q6c

The distance Simon drives each day can be represented by the rule Tn=220(1.06)n1T_n = 220(1.06)^{n-1}.

Q6e

The approximate distance from Sydney to Alice Springs is 2770 km and from Perth to Alice Springs is 2550 km.

Q6a
2 marks

Write a recursive rule to model the distance Josh drives each day.

Q6b
1 mark

Calculate how far Josh is away from Sydney by the end of day four.

Q6c
2 marks

Interpret what the numbers 220 and 1.06 represent in the context of the question.

Q6d
3 marks

Determine the day and date when Simon drove 330.8 km.

Q6e
3 marks

Determine who is the first to arrive in Alice Springs. Justify your answer.

Q6f
2 marks

After Josh and Simon meet in Alice Springs, they drive together to Darwin. The distance they travel each day can be represented by the rule Tn+1=aTn+bT_{n+1} = aT_n + b.

Given they travel 380 km on day one, 309 km on day two and 269.95 km on day three, determine the value of aa and bb.

Q3
2023
SCSA
Paper 1
9 marks
Q3

From January 1, 2020, a company offered its employees an income package with a starting wage of $4000 per month, paid at the end of each month. Also, as an incentive to stay with the company, there was a monthly increase of $50 each month.

Q3a
2 marks

Determine a recursive rule for the monthly wage.

Q3b
2 marks

Deduce a simplified rule for the nnth term of the monthly wage.

Q3c
2 marks

Determine the monthly wage for December 2020.

Q3d
3 marks

The company has decided to make the monthly increase $60 from the end of December 2023.

Calculate the monthly wage for March 2024.

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