You were recently hired as an intern at a local machine shop. The head machinist hands you a bag of hardware, which he knows to contain 29 pieces of 1/4"-20 bolts and 17 pieces of 1/4"-28 bolts, all of varying lengths. You reach into the bag and randomly (i.e, without looking) select a bolt, which you place on a workbench. What is the probability that you picked a 1/4"-20 bolt?