When simplified the answers results in
= -1
pi·(7.2/2)^2·x = 2·pi·(7.2/2)^2 + 2·pi·(7.2/2)·x
x = 4.5 = 4 1/2
O = V = 1458/25·pi = 58.32·pi
To get the probability that at least 8 of the words on the test are words that students know we need to do the following calculations.
<span>=[C(16,8)*C(10,2) + C(16,9)*C(10,1) + C(16,10)*C(10,0)] / C(26,10)
</span>
=0.132
If I remember how to do this right I’m pretty sure you just divid by 178.90 by 5.75 wich gives you 31.11 for the tax rate