Make a circle and then another circle. There should be a oval in the middle.
Like this:
https://docs.google.com/drawings/d/10jIdkQW5rnxfDS9T2WeqkwRTvl92oJsYkXVLj8Zn6hU/edit
<span>3 of the 20 toothbrushes are defective, so the initial probability of selecting a defective toothbrush on the first try is 3/20. After that, there will be 2 defective toothbrushes in the remaining 19, so the probability of selecting one of those on the 2nd try will be 2/19. To get the probability of those two events happening sequentially, we multiply the two probabilities. Thus (3/20)*(2/19) = 6/380 = 0.0157, or about 1.6%.</span>
R - 6m = n.....add 6m to both sides
r = n + 6m <==
3 sqrt (6) should be correct
