Why is the base of parallelogram 1/2 the circumference of the circle

The brain volumes (cm cubed) of 50 brains vary from a low of 904 cm cubed to a high of 1488 cm cubed. use the range rule of thumb to estimate the standard deviation s and compare the result to the exact standard deviation of 175.5 cm cubed, assuming the estimate is accurate if it is within 15 cm cubed

How do the number line graphs of the solutions sets of -23 > x and x-23 differ?

This is about circle theorems. someone asap : (