If a train goes at constant speed of 40 miles per hour for one hour, then at constant speed of 55 miles per hour for two hours, what is its average speed at the train?

because the train goes 72 mph for 2 hours

Explanation:

does the train go 72mph for 2 hours as well? if so the answer would be 324 because you have to add 90 twice scene it goes at that speed for 2 hours thats 180. assuming  the train goes 72 mph for 2 hours it would be 144. then add 180 and 144 and you get 324 merry christmas and a happy newyear to you and your family

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.