This is a "lab" activity where students are given equations for two different waves along with a large sheet of butcher paper. From there they are tasked with drawing a scale, calculating points for the given waves, plotting the given waves, calculating points for the superimposed wave, plotting the superimposed wave, and identifying different key points on the superimposed wave, like areas of constructive and destructive interference and the equilibrium position.
I give each group a piece of butcher paper, a meter stick, a calculator, and some markers and then set them free to complete their poster. There are sheets for six different groups so not all groups will be plotting the exact same waves.
On average, I'd say this takes about an hour, but some groups will take longer, other will finish sooner. Once each group is done, I give them masking tape and have them go hang them on the wall outside the classroom, where I can later walk around with a clipboard to grade them. :)