The value of 5 in 500 is times the value of 5 in 50

Brent wants to know what is 5 x 1/2

Just tell me how to set up the equation.

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