Answer:
602.88cm²
Step-by-step explanation:
Find the image of the cylinder attached
Surface area of a cylinder = A=2πrh+2πr²
r is the radius = 4cm
Height h = 20cm
Substitute
A = 2πr(r+h)
A = 2π(4)(4+20)
A = 8π(24)
A = 192π
A = 192(3.14)
A = 602.88cm²
Hence the surface area of the cylinder is 602.88cm²
Answer:
90 g of water should be added and he will make 900 g of solution.
Step-by-step explanation:
Let x g be the amount of salt Ilya add to 810g of water to make 10% solution. Then 810+x g is the amount of new solution. Thus,
810+x - 100%,
x - 10%.
Mathematically,

So 90 g of water should be added and he will make 810+90=900 g of solution.
The formula for volume of a cylinder is:
Volume = PI x r^2 x h, where r is the radius and h is the height.
Volume = PI x 18^2 x 40
Volume = PI x 324 x 40
Volume = PI x 12,960
The exact volume would be 12,960PI cubic ft.
The decimal answer would vary depending on what value of PI is used.
Two numbers that add together to get 0 are called additive inverses of each other.