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The number of gannets on an island is assumed to follow this exponential growth model - OCR - GCSE Maths - Question 21 - 2018 - Paper 4

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The number of gannets on an island is assumed to follow this exponential growth model. $$N = 0.45 \times 1.07^x$$ $N$ is the number of gannets, in thousands. $x$ i... show full transcript

Worked Solution & Example Answer:The number of gannets on an island is assumed to follow this exponential growth model - OCR - GCSE Maths - Question 21 - 2018 - Paper 4

Step 1

Complete the table for N = 0.45 × 1.07^x.

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Answer

To complete the table, we will calculate the values of NN at each specified xx using the formula:

N=0.45×1.07xN = 0.45 \times 1.07^x

  1. For x=0x = 0: N=0.45×1.070=0.45×1=0.45N = 0.45 \times 1.07^0 = 0.45 \times 1 = 0.45 Therefore, N=0.45N = 0.45.

  2. For x=5x = 5: N=0.45×1.0750.63N = 0.45 \times 1.07^5 \approx 0.63

  3. For x=10x = 10: N=0.45×1.07101.00N = 0.45 \times 1.07^{10} \approx 1.00

  4. For x=15x = 15: N=0.45×1.07151.25N = 0.45 \times 1.07^{15} \approx 1.25

  5. For x=20x = 20: N=0.45×1.07201.74N = 0.45 \times 1.07^{20} \approx 1.74

Thus, the completed table is:

xx05101520
NN0.450.631.001.251.74

Step 2

Draw the graph of N = 0.45 × 1.07^x.

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Answer

To draw the graph of the function N=0.45×1.07xN = 0.45 \times 1.07^x, follow these steps:

  1. Plot the points calculated from the table on a grid:

    • (0, 0.45)
    • (5, 0.63)
    • (10, 1.00)
    • (15, 1.25)
    • (20, 1.74)
  2. After plotting these points, connect them smoothly to illustrate the exponential growth characteristic. Ensure the curve smoothly approaches the plotted points while reflecting the growth model.

  3. Label the axes appropriately: The horizontal axis for ‘Number of years, xx, after 1^{st} January 2010andtheverticalaxisforNumberofgannets,’ and the vertical axis for ‘Number of gannets, N$, (thousands)’. This will help in visualizing the growth of the gannet population.

  4. Ensure that you maintain a consistent scale on both axes.

Step 3

Use the graph to find the year when the gannet population is predicted to reach 1000.

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Answer

To find when the gannet population reaches 1000 (or N=1.00N = 1.00 in thousands), locate N=1.00N = 1.00 on the vertical axis of the graph. Draw a horizontal line from this point until it intersects the curve.

Drop down vertically to see the corresponding value of xx on the horizontal axis. Based on the graph, assume you find that this occurs at approximately x=11.5x = 11.5. Given that the model starts from 1st^{st} January 2010, you can calculate the year:

2022=2010+12ext(roundedtothenearestfullyear)2022 = 2010 + 12 ext{ (rounded to the nearest full year)}

Therefore, the gannet population is predicted to reach 1000 in the year 2022.

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