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#### karush

##### Well-known member

- Jan 31, 2012

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**IBP9 An urban highway has a speed limit of 50 km/ h**

View attachment 1217

(a) assume the $km\ h^{-1}$ means $\displaystyle\frac{km}{h}$

$30\%$ on Z-table is $\approx 0.53$

so using $\displaystyle\frac{X-\mu}{\sigma}=Z$ then $\displaystyle\frac{50-44.8}{10}=0.53$

(b) (c) (d) to come

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