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    I'm stuck on part ii

    On part i) I got = 20.33%

    for part ii)

    This is what I've attempted:

    p(z< (x-85)/sqrt(36) = 0.25

    then I used inverse normal distribution tables for 0.75 (as 1-0.25=0.75) to get 0.6745

    so (x-85)/6 = 0.6745

    but the answer is wrong, as it is meant to be 81g
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    You've made two little slips: the first is that you need a negative number from the inverse normal, because you're looking for a probability less than 1/2; the second is that you've used x-(85/6) rather than (x-85)/6.
 
 
 
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