Given data:
Mean: 84 lb
Standard deviation: 12lb
Find % of hippos born weighing 25 poind or less.
1. Find the z-score corresponding to x=25:
[tex]\begin{gathered} z=\frac{x-\mu}{\sigma} \\ \\ z=\frac{25-84}{12} \\ \\ z=-\frac{59}{12} \\ \\ z=-4.92 \end{gathered}[/tex]
2. Use a z-table to find the probability of x less or equal to 25 (z-score -4.92):
For a z-score of -3.50 or less the corresponding value is 0.0001
[tex]P(x\leq25)=0.0001[/tex]
3. Multiply by 100 the value you get in step 2 to get the percentage:
[tex]0.0001*100=0.01[/tex]Then, the percentaje of hippos born weighing 25 poind or less is 0.01%
