Answer:
1. r = 2.82 cm
h = 5.6 cm
The maximum volume possible to the nearest 10 mL = 140 mL
2. Size side of square base of box is 5.64 cm
Height of box = 5.6 cm
The surface area of the box is 189.96 cm²
The volume of the box is 178.13 cm³
3. The procedure for solving the problem was through noting that the shape of the cross-section of the pyramid is an isosceles triangle ans also that smallest possible box for the pretty perfume is one which fits the angle of inclination of the lid. This was found out by initially using the combined height of the perfume and the lid (placed to fit the spherical outline of the bottle) to calculate the dimensions of the pyramid, from which it was observed that the angle of inclination of the lid is larger than that of the calculated dimension, such that the lid outline would be visible and could eventually tear the perfume box
With the inclination angle, β, which is the base angle of the isosceles triangle, the angle at the top of the pyramid cross-section is calculated and the following relations are used to calculate the triangular cross-section of the pyramid
h = a·cos(α/2)
b = 2·a·cos(β)
With the calculated dimensions, a, b, and h the area, A, of the square pyramid is calculated as 2×b×a + b² and the volume, V, as 1/3×b²×h
The attached diagram shows the the cross-section of the perfume in the pyramid box.
Step-by-step explanation:
1. The surface area of the cylinder = 2πr² + 2πrh = 150 cm².........(1)
The volume of the cylinder, V = πr²h = 100 mL = 100 cm³..............(2)
From equation (2), h = 100/(π·r²)
Substituting the value if h in equation (1), we have;
2πr² + 2πr100/(π·r²) = 150
2πr² + 200/r = 150
(2πr³ + 200)/r = 150
2πr³ + 200 = 150×r
2πr³ -150·r+ 200 = 0
150 = 2πr² + 2πrh
h = (150 - 2πr²)/(2πr)
h = (75- πr²)/(πr)
Substituting the value of h in the equation for the volume, we have;
V = πr²h = πr²(75- πr²)/(πr)
V = 75·r - π·r³
At maximum volume, dV/dr = 0, we have
d(75·r - π·r³)/dr = 75 - 3·π·r²= 0
3·π·r²= 75
π·r² = 25
r = 5√π/π
h = (75- πr²)/(πr) = (75- π(5√π/π)²)/(π(5√π/π)) = (75 -25)/(5·√π)
h = 50/(5·√π)= 10·√π/π
The maximum volume = πr²h = π×25/π×10·√π/π = 250·√π/π = 141.05 cm³
The maximum volume possible = 141.05 cm³ = 141.05 mL
The maximum volume possible to the nearest 10 mL = 140 mL
The dimensions of the bottle are;
r = 2.82 cm
h = 5.6 cm
The surface area of the bottle = 2π(2.82)² + 2π×2.82 ×5.6 = 149.2 cm
2
Given that the cylindrical bottle has r = 2.82 cm and h = 5.6 cm, we have;
Size side of square base of box = 2 × 2.82 = 5.64 cm
Height of box = 5.6 cm
The surface area of the box = 2 × Area of base + 4 × Area of side
The surface area of the box = 2 *5.64^2 + 4 * 5.6 * 5.64 = 189.96 cm²
The volume of the box = Area of base × Height = 5.64^2*5.6 = 178.13 cm³
3. Diameter of spherical bottle = 7 cm = 2×r
Volume of the sphere bottle = 4/3πr³ = 4/3*3.5^3*π = 343/6·π = 179.6 cm³
The surface area of the sphere bottle = 4πr² = 4*(7/2)^2*π = 49·π = 156.94 cm²
3 i. The volume of a cone = 1/3πr²h = 1/3*(5/2)^2*4.5 = 9.385·π = 29.45 cm³
The surface area of a cone = πrS
S = √(4.5^2 + (5/2)^2) = 5.15
The surface area of a cone = π*2.5*5.15 = 40.43 cm²
3 ii. The depth of fitness of the lid on the bottle = 7/2 - √(7/2)^2 - 2.5^2) = 1.05
The total height of the spherical bottle with the conical lid = 7 + 4.5 - 1.05 = 10.45 cm
3 iii. Given that the box is shaped like a pyramid we have;
Width of the box at middle of the height of the spherical bottle = 7 cm
Height of the box = 10.45 cm
With the aid of a graphing calculator, the width of the square pyramid is found to be 12.12 cm
The volume = 1/3*12.12^2*10.45 = 511.68 cm²
The surface area = 2*12.12*√(12.12/2)^2 + 10.45^2) +12.12²= 439.7 cm²
The angle of inclination of the lid = tan⁻¹ (4.5/2.5) = 60.95°
The angle of inclination of the calculated box is tan⁻¹ (10.45/6.06) = 59.88
Since the lid is steeper, we make use of the angle of the lid
The base angles are thus = 60.95°
The angle at the top is thus 180 - 60.95*2 = 58.11°
Therefore, by the formula, we find that
a = 12.25 cm
b = 11.897 cm
h = a·cos(α/2)
h = 10.707 cm
The volume = 1/3*11.897^2*10.707 = 505.15 cm³
The surface area = 2*11.897*√(11.897/2)^2 + 10.707^2) +11.897²= 432.98 cm²
The angle at the top of the box = 2