3. The disk in a computer starts to spin and spins up to 5400 rpm in 1.5 seconds

3600 rpm per second

Explanation:

5400:1.5

Divide both sides by 1.5

3600:1

the skeletons of most mammals reach a certain size and then stop growing. however, many animals, including some mammals, keep growing throughout their lives. kangaroos, for example, just keep growing and growing until they die. also, the longer an animal lives the greater the chance it might catch some deadly disease.