Question 926925
mean = 320mi, standard deviation is 80 
sample: n = 40
a) SE = 80/sqrgt(40) = 6.325 rounded
z = (x - 320)/6.325
b) P(x > 320) = P(z > 0) = .50 0r 50%
c) P(320< x < 350) = P( 0 < z < 30/6.325) = P(z < .4216) - P(z < 0) = .6633-.5 = .1633
0r  Using a TI calculator 0r similarly a Casio fx-115 ES plus
P( 0 < z < 30/6.325) = normalcdf(0,.4216)= .1633 0r 16.33%
d )p(x > 350) = P(z > .4216) = normalcdf(.4216, 100)= .3367 0r 33.67%