Answer:
- about 243.9 cm³
- 35828 4/7 cm² = 3 102/175 m²
Step-by-step explanation:
1.
The 8-cm diameter sphere has a radius of 4 cm. The volume of it is given by ...
V = 4/3πr³ = 4/3π(4 cm)³ = 256/3π cm³
The 8-cm cube has a volume of ...
V = s³
V = (8 cm)³ = 512 cm³
The volume of the empty space is the difference of these volumes:
space = 512 cm³ -256/3π cm³ = 256(6 -π)/3 cm³
space ≈ 243.9 cm³
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2.
The area of a hemisphere is twice the area of a circle with the same radius. Then the area of the top and bottom of the birdbath will be 2+1 = 3 times the area of a circle with radius 30 cm.
top+bottom area = 3 × πr² = 3 × 22/7(30 cm)² = 8485 5/7 cm²
The lateral area of the cylinder is ...
LA = 2πrh
= 2(22/7)(30 cm)(145 cm) = 27342 6/7 cm²
Then the total surface area of the birdbath is ...
total area = top+bottom area + lateral area
total area = 8485 5/7 cm² +27342 6/7 cm² = 35828 4/7 cm²
= 3 102/175 m²
