Question

A certain variety of pine tree has a mean trunk diameter of 150 cm and a standard deviation of 30 cm. Approximately what percent of these trees hava diameter greater than 210 cm?a)2.35% b)2.5%b) 13.5%c) 71.4%

Answer 1

Solution

$\begin{gathered} Probability(x>210) \\ P(x>210)=1-(\frac{210-150}{30}) \\ =1-p(2) \end{gathered}$$\begin{gathered} 1-(0.15\text{\%+2.35\%+13.5\%+34\%+34\%+13.5\%\rparen} \\ (1-97.5\text{ \%\rparen} \\ =2.5\text{ \%} \end{gathered}$

Therefore the percent of the trees with diameter greater than 210cm

= 2.5%

Hence the correct answer is Option B