Bacteria are growing in a circular colony one bacterium thick. the bacteria are growing at a constant rate, making the area of the colony increase at a rate of 12mm^2 per hour. How fast is the radius changing when the radius is 3mm?

Answer 1

A = pi r^2
dA/dt = pi (2r) dr/dt
12 = pi (2*3) dr/dt
dr/dt = 2/pi mm/hr

Answer 2

The length of a telescope has a radius of 1 meter what is the len's circumference use 3.14 for