Find the perimeter and the area. I need help ASAP

What is the least common multiple for 6 and 8? what is the least common multiple for 4 and 12 ? what is the least common multiple for 11 and 12? what is the least common multiple for 3 and 6?

Aconstruction worker needs to put a rectangular window in the side of a building he knows from measuring that the top and bottom of the window have a width of 8bfeet and the sides have a length of 15 feet he also measured one diagonal to be 17 feet what is the length of the other diagonal

Atoss of a 20-sided die is equally likely to be any integer between 1 and 20 inclusive. what is the variance? provide your answer to two decimal points.