4 out of 5 dentists prefer a new mouthwash

Question

If 5 dentists are chosen at random from the phone book, what is the approximate probability that exactly 3 of them will prefer the new mouthwash?
 
A) 0.014
B) 0.051
C) 0.173
D) 0.205

Answer 1

probability(prefer mouth wash) = 4/5

 

use binomial calculation:

choose(5,3)*(4/5)^3*(1/5)^2 = 128/625 = 0.2048

 

answer -> D 0.205