Answer
0.0185
Work Step by Step
Let X denote the number of failed ball bearings.
Number of trials n= 11,
Probability of success p = 0.10
Probability of failure q= 1-p= 0.90
For breaking down, X should be at least 4.
P(X≥4)= 1-P(X=3)-P(X=2)-P(X=1)-P(X=0)
$= 1-(^{11}C_{3}(0.10)^{3}(0.90)^{8})-(^{11}C_{2}(0.10)^{2}(0.90)^{9})-(^{11}C_{1}(0.10)^{1}(0.90)^{10})-(^{11}C_{0}(0.10)^{0}(0.90)^{11}= 0.0185$
