First things first you're going to want to find out how many inches are in 11.9 feet and how many hours are in 3 days. 11.9*12=142.8, so there are 142.8 inches in 11.9 feet. 3*24=72, so there are 72 hours in 3 days. Now, divide 142.8 by 72 to find out how many inches it grows per hour. 142.8/72= about 1.983333... . Round that to the nearest hundredth, and you get 1.98. The tropical giant bamboo grows about 1.98 inches per hour.
