Question 1086323
a) Calculate the z scores for both races.
{{{z[1]= (46-48.1)/6.2 }}}
{{{z[2]= (43.2-45.7)/7.8 }}}
The lower the z score, the better the placement.
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b) Find the probability using {{{z[2]}}} then multiply that value by the number of runners. Run up or down appropriately. 
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c) Find z such that {{{P(z[25])=0.25}}}
{{{P(z[25])=0.25}}}
{{{z[25] =-0.67449 }}}
So,
{{{(X[25]-45.7)/7.8 =-0.67449 }}}
Solve for {{{X[25]}}}.