The '68-95-99.7 ' rule says,
-About 68% of values fall within one standard deviation of the mean.
-About 95% of the values fall within two standard deviations from the mean.
-Almost all of the values — about 99.7% — fall within three standard deviations from the mean.
Here
[tex] 27.8=29-1*1.2 [/tex]
The length falls within one standard deviation of the mean.
Therefore, the probability [tex] P(27.8<L<30.2)=0.68 [/tex]
The required probability is
[tex] P(L<27.8)=\frac{1-0.68}{2}=0.16 [/tex]
