# Math Help - Help on statistics past paper questions pls?

1. ## Help on statistics past paper questions pls?

2. Originally Posted by arthus123
Posted this in wrong section before so here it is.

Past exam paper Qs picture by nuclearone - Photobucket

Thanks, help greatly appreciated
(a) $\overline{X}$ ~ Normal $\left( \mu = 30, ~ \sigma = \frac{2.5}{\sqrt{100}} = 0.25\right)$.

Calculate $\Pr(29.5 < \overline{X} < 30.5)$.

(b) $0.4 = z_{0.025} \frac{2.5}{\sqrt{n}}$. Solve for $n$.

3. Thank you mr. fantastic! :O