Answer
$P(X\geq140)=0.0009$
If we randomly select 10,000 samples of 250 Americans 18 years old or older, we would expect to find about 9 samples in which at least 140 read at least six books within the past year.
Work Step by Step
$μ_X=np=250\times0.46=115$
$σ_X=\sqrt {np(1-p)}=\sqrt {250\times0.46(1-0.46)}=7.88$
Let's find the z-score for 139.5:
$z=\frac{X-μ}{σ}=\frac{139.5-115}{7.88}=3.11$
According to Table V, the area to the left of the standard normal curve for a z-score equal to 3.11 is 0.9991.
But, we want the area to the right (at least 140) of the standard normal curve for a z-score equal to 3.11:
$1-0.9991=0.0009$
