For linear relationships, the consecutive values of y would increase or decrease by a constant value. For exponential relationships, the ratio of consecutive values of y would always be constant.
Looking at the given table, the values of y are the amount of cobalt-56 remaining in grams.
760/1000 = 0.76
578/760 = 0.76
We can see that the ratio of consecutive y values is constant.
Therefore, the table is exponential.
The rate of change is the same the ratio of the difference between consecutive values of y to the previous value of y
Rate of change = (1000 - 760)/1000 = 240/1000 = 0.24
Percentage change = 0.24 * 100 = 24%