How many times must john run around a 1/4 mile track to run 2 1/2 miles?

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 long must $542 be invested at a rate of 7% to earn $303.52 in interest? in a easier way

Given the two similar triangles, how do i find the missing length? if a=4, b=5, and b'=7.5 find a'