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Alex invests £4500 at a rate of 7.5% per year simple interest - OCR - GCSE Maths - Question 4 - 2023 - Paper 4

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Alex invests £4500 at a rate of 7.5% per year simple interest. (a) Find the value of the investment at the end of 4 years. (b) At the end of t years, the value of ... show full transcript

Worked Solution & Example Answer:Alex invests £4500 at a rate of 7.5% per year simple interest - OCR - GCSE Maths - Question 4 - 2023 - Paper 4

Step 1

(a) Find the value of the investment at the end of 4 years.

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Answer

To calculate the value of the investment at the end of 4 years using simple interest, we can use the formula:

A=P(1+rt)A = P(1 + rt)

where:

  • AA is the total amount after time tt,
  • PP is the principal amount (£4500),
  • rr is the rate of interest (7.5% per year or 0.075 as a decimal),
  • tt is the time in years (4 years).

Substituting the values into the formula:

A=4500(1+0.075×4)A = 4500(1 + 0.075 \times 4)

Calculating this:

  1. Calculate the interest: 0.075×4=0.30.075 \times 4 = 0.3.
  2. Now calculate AA:
    A=4500(1+0.3)=4500×1.3=5850.A = 4500(1 + 0.3) = 4500 \times 1.3 = 5850.

Thus, the value of the investment at the end of 4 years is £5850.

Step 2

(b) Find the value of t.

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Answer

For the investment to exceed £13500, we will use the same formula for simple interest:

A=P(1+rt)A = P(1 + rt)

Setting AA to £13500 and solving for tt:

13500=4500(1+0.075t).13500 = 4500(1 + 0.075t).

  1. Divide both sides by 4500: 135004500=1+0.075t\frac{13500}{4500} = 1 + 0.075t 3=1+0.075t3 = 1 + 0.075t

  2. Subtract 1 from both sides: 2=0.075t2 = 0.075t

  3. Divide both sides by 0.075: t=20.075=26.67.t = \frac{2}{0.075} = 26.67.

Therefore, the value of tt is approximately 26.67 years.

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