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The diagram shows a sector of a circle with centre O, radius 8 cm and sector angle 165 degrees. (a) Calculate the total perimeter of the sector. (b) The surface area of a sphere is the same as the area of the sector. Calculate the radius of the sphere.
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18. (d) Adam earned $36 515 in 2019. This was an increase of 9% on his earnings in 2018. Work out his earnings in 2018.
Step 1: Understand the relationship between 2018 and 2019 earnings.
If Adam's earnings increased by 9% in 2019, his 2019 earnings represent 100% + 9% = 109% of his 2018 earnings.
Let be his earnings in 2018.
Step 2: Calculate his earnings in 2018.
We are given E_{2019} = \36,515.
$$\36,515 = E_{2018} \times 1.09E_{2018} = \frac{$36,515}{1.09}E_{2018} = $33,500$$
Adam's earnings in 2018 were \boxed{\33,500}$.
19. The diagram shows a sector of a circle with centre O, radius 8 cm and sector angle 165°.
Part a· 2 steps
Calculate the total perimeter of the sector.
Calculate the length of the arc.
The formula for arc length is .
Given and cm.Calculate the total perimeter of the sector.
The perimeter of the sector is the sum of the arc length and two radii.
PerimeterRounding to one decimal place:
The total perimeter of the sector is .
Part b
The surface area of a sphere is the same as the area of the sector. Calculate the radius of the sphere. [The surface area, A, of a sphere with radius r is ]
Calculate the area of the sector.
The formula for the area of a sector is .
Given and cm.Set the area of the sector equal to the surface area of the sphere.
Let be the radius of the sphere. The surface area of the sphere is .
Solve for the radius of the sphere, .
Divide both sides by :
Divide both sides by 4:
Rounding to two decimal places (or 3 significant figures):
The radius of the sphere is .
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