David can complete 4 math problems in 15 minutes. He has 20 math problems to do. How long will it take him to finish his test?

75 min or 1 hour and 15 min

Step-by-step explanation:

15/4

=3.75

3.75*20

=75

answer: the answer is (b) amie should have multiplied

step-by-step explanation: given a sphere and a cylinder with same radius and height.

let, 'r' be the radius of the cylinder and sphere and 'h' be the height of the cylinder. according to the question,

r = h.

now, the volume of the sphere will be

and the volume of the cylinder will be

therefore, we have

thus, ammie should have multiplied the volume of the sphere