How can you tell if a number is devisible by 3?

On a architect's drawing of a house, 1 inche representa 1.5

Television sizes are based on the length of the diagonal of the television's rectangular screen. so, for example, a 70-inch television is a television having a diagonal screen length of 70 inches. if a 70 inch television's diagonal forms a 29°angle with the base of the screen, what is the vertical height (1) of the screen to the nearest inch? 70 inhin

Is the power produced directly proportional to the wind speed, give reasons for your answer?