The Brandywine River is at its flood stage of 9 ft. It’s continuing to rain. The next measurement shows that the river has risen 1 1/2 ft. ft. An additional measurement shows that the river has risen 1 5/12 ft. ft. How many more feet does the river need to rise to be at the major flood stage of 13 ft.? Express your answer in simplest.
The river has already risen by 1 1/2 ft + 1 5/12 ft = <<1 1/2+1 5/12=2 7/12>>2 7/12 ft.
To reach the major flood stage, the river needs to rise an additional 13 ft - (9 ft + 2 7/12 ft) = 13 ft - 9 ft - 2 7/12 ft = 1 5/12 ft.
In simplest form, this is equal to <<1 5/12=1 5/12>>1 5/12 ft. Answer: \boxed{1 \frac{5}{12}} ft.