The number of gannets on an island is assumed to follow this exponential growth model - OCR - GCSE Maths - Question 21 - 2018 - Paper 4
Question 21
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 N at each specified x using the formula:
N=0.45×1.07x
For x=0:
N=0.45×1.070=0.45×1=0.45
Therefore, N=0.45.
For x=5:
N=0.45×1.075≈0.63
For x=10:
N=0.45×1.0710≈1.00
For x=15:
N=0.45×1.0715≈1.25
For x=20:
N=0.45×1.0720≈1.74
Thus, the completed table is:
x
0
5
10
15
20
N
0.45
0.63
1.00
1.25
1.74
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=0.45×1.07x, follow these steps:
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)
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.
Label the axes appropriately: The horizontal axis for ‘Number of years, x, after 1^{st} January 2010’andtheverticalaxisfor‘Numberofgannets,N$, (thousands)’. This will help in visualizing the growth of the gannet population.
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=1.00 in thousands), locate N=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 x on the horizontal axis. Based on the graph, assume you find that this occurs at approximately x=11.5. Given that the model starts from 1st January 2010, you can calculate the year:
2022=2010+12ext(roundedtothenearestfullyear)
Therefore, the gannet population is predicted to reach 1000 in the year 2022.