How do I determine how fast my son shoots a hockey puck?

He is doing a science project for school. We did several shots from the blue line (60 feet to the goal line, then another 12 to the boards - so 72 feet total distance). It took him .9 seconds from the time he hit the puck until it hit the boards. I know that MPH is figured using distance divided by time. SO in my feeble calculations, he would shoot the puck 80 mph. Is this correct?