Solve the following proportion r/5=9/21

An elevator travels 310 feet in 10 seconds. at that speed, how far can't his elevator travel in 12 seconds?

240 seventh graders and two-thirds of the students participate in after-school activities how many students participate in after-school activities

If you were constructing a triangular frame, and you had wood in the length of 4inches, 4 inches, and 7 inches, would it make a triangle? would you be able to create a frame from these pieces of wood? yes or no. explain your mathematical thinking