Awater tank has the shape of an inverted cone (like an ice cream cone without ice cream). the tank is 10m high and has a radius of 3m at the top. if the water is 5m deep (in the middle), what is the surface area of the top of the water?

we know that

the surface area of the top of the water is calculated with the formula of the area of a circle

Step 1

Find the radius of the water tank in the middle of the tank

by proportion

so

For h=5 m

the radius is equal to r=1.5 m

Step 2

Find the surface area

therefore

the answer is

the surface area of the top of the water is