# Math Help - Lung Capacity(mean,standard deviation)

1. ## Lung Capacity(mean,standard deviation)

A biology teacher recorded the lung capacity of each 16 year old in her school. The eacher determined that the values were normally distributed with a mean of 3500 ml and a standard deviation of 300 ml. If 23 percent of the 16 year olds lung capacities were less than samanthas,what was samanthas lung capacity?

2. Originally Posted by dan123
A biology teacher recorded the lung capacity of each 16 year old in her school. The eacher determined that the values were normally distributed with a mean of 3500 ml and a standard deviation of 300 ml. If 23 percent of the 16 year olds lung capacities were less than samanthas,what was samanthas lung capacity?
Hi dan123,

Let X be the lung capacity.
We know that $P(X< \text{samanthas})= 0.23$
Let S be samanthas capacity:
$P(Z< \frac{S-3500}{300})=0.23$
From the table, I get -0.74, do check again, I'm bad at looking up the table.

$\frac{S-3500}{300}=-0.74$
Solve S.