Grade 11 Maths · Financial Maths

Find i and n per period

Find the rate per period and the number of periods, for example 9% a year paid monthly for 4 years gives i = 0,09 ÷ 12 and n = 48.

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Question 7.3 · May/June 2025 · Paper 1 · National (DBE) · 6 marks

7.3 On 1 March 2021, Abby made a once-off deposit of

R 12000

into an account earning interest at a rate of

9, 5%

p.a., compounded monthly. She deposited

R 500

into the same account on 1 April 2023 and continues to make these monthly deposits of

R 500

on the first day of each month thereafter. Calculate how much money was in the account immediately after the deposit of

R 500

is made on 1 March 2025, exactly four full years after her initial deposit.(6)

Work it out on paper first. Then mark yourself with the official memo, one tick at a time.

More past paper questions: find i and n per period

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3. Question 7.1 · November 2024 · Paper 1 · National (DBE) · 3 marks
7.1 Mary's grandparents deposited R5 000 into a savings account on the day that she was born. The account pays interest at a rate of 6,8% p.a., compounded quarterly. Calculate the accumulated amount in this account on Mary's $1 6^{th}$ birthday.(3)
Show the memo (3 ticks)Memo
1. ✓
  Identify parameters $P = 5000$ ; $i = \frac{6 , 8}{400} = 0, 017$ ; $n = 16 \times 4 = 64$
  1 mark · Find i and n per period
2. ✓
  Substitute into compound interest formula $A = 5000 (1 + \frac{0 , 068}{4})^{64}$
  1 mark · Use the compound interest formula
3. ✓
  Calculate final amount $A = R 14706, 56$
  1 mark · Use the compound interest formula
4. Question 8.3.1 · November 2023 · Paper 1 · Provincial · 5 marks
8.3 Lwandi made an initial deposit of R23 000 into an investment account that paid an interest rate of $9, 25%$ compounded quarterly. After 3 years since the start of his investment, he deposited R13 500 and the interest rate changed to $8, 2%$ p.a. compounded monthly. Exactly 5 years after his initial deposit, Lwandi withdrew R9 000.

Answer the questions that follow.
8.3.1 Calculate the total value of the investment in Lwandi's account at the end of the 5th year.(5)
Show the memo (5 ticks)Memo
1. ✓
  $i$ and $n$ for the first 3 years $i = \frac{0 , 0925}{4}$ and $n = 12$
  1 mark · Find i and n per period
2. ✓
  $i$ and $n$ for the last 2 years $i = \frac{0 , 082}{12}$ and $n = 24$
  1 mark · Find i and n per period
3. ✓
  Value after 3 years plus deposit $(23000 (1 + \frac{0 , 0925}{4})^{12} + 13500)$
  1 mark · Use the compound interest formula
4. ✓
  Growth for the last 2 years $\times (1 + \frac{0 , 082}{12})^{24}$
  1 mark · Use the compound interest formula
5. ✓
  Answer $A =$ R51 530,18
  1 mark · Use the compound interest formula
5. Question 8.1 · November 2025 · Paper 1 · Provincial · 3 marks
8.1 A motorbike costs R250 000 and depreciates by 13% p.a. annually, calculated on the reducing balance method.

Calculate what the motorbike will be worth after 6 years.(3)
Show the memo (3 ticks)Memo
1. ✓
  $n = 6$ $A = P (1 - i)^{n}$ with $n = 6$ , $i = 0, 13$
  1 mark · Find i and n per period
2. ✓
  Substitution $= 250000 (1 - 13%)^{6}$
  1 mark · Calculate depreciation
3. ✓
  Answer $=$ R108 406,55
  1 mark · Calculate depreciation
6. Question 7.2.1 · September 2024 · Paper 1 · Provincial · 3 marks
7.2 Micaela buys furniture to the value of R10 000. She borrows the money on 1 February 2023 from a financial institution that charges interest at a rate of 9,5% p.a. compounded monthly. Micaela agrees to pay monthly instalments of R450. The loan agreement allows Micaela to start paying equal monthly instalments from 01 August 2023.
7.2.1 Calculate the total amount owing to the financial institution on 1 July 2023.(3)
Show the memo (3 ticks)Memo
1. ✓
  Substitute into correct formula $A = 10000 (1 + \frac{0 , 095}{12})^{5}$
  1 mark · Use the compound interest formula
2. ✓
  Correct i and n $i = \frac{0 , 095}{12}; n = 5$
  1 mark · Find i and n per period
3. ✓
  Answer $R 10402, 15$
  1 mark · Use the compound interest formula

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