a circular sinkhole has a circumference of 75.36 meters. a week later, it has a circumference of 150.42 meters. estimate the diameter of the sinkhole each week

There may be more than one answer for this.......according to whether the growth rate is considered to be lnear, exponential, etc.

Assuming it's linear, the circumference changes by [150.42- 75.36] / [2 - 1]  = 75.06 in each week