Answer:
The interval [25, 35] has the slowest average rate of decay.
Step-by-step explanation:
The number of grams in a sample of radium is represented by the function [tex]r(t) = 50\cdot e^{-0.013\cdot t}[/tex], which is a monotonous decreasing function. Hence, the greater the values of [tex]t[/tex], the slowest the average rate of decay, represented by a secant line. The interval [25, 35] has the slowest average rate of decay.