the answer to this question would be 12 and 1/8
Answer:
The formula to calculate standard deviation from probability is \sqrt(n*p*(1-p)). n is the sample size, and 200 in this case (number of putts for practice). p is 80% or 0.8, the probability that he can make it. So the standard deviation is \sqrt(200*0.8*(1-0.8)=\sqrt(200*0.8*0.2)=\sqrt(16)=4.
If they only have 30.25, then they still need 39.50
The answer to your question is -2+ square root 19 /3 100%