



 
Hi Jenny, The answer you sent for the first question was
I agree with everything except the last step. From the standard normal table P(0 < Z < 0.43) = 0.1664 and you want P(Z > 0.43) = P(0 < Z)  P(0 < Z < 0.43) = 0.5  0.1664 = 0.3336. You have a similar error in the second two parts. For the last question you want to find k so that P(X > k) = 0.20 which converts to P( (X  μ)/σ > (k  27)/7) = P(Z > (k  27)/7) = 0.20. Hence you want to find k so that P(0 < Z < (k  27)/7) = 0.5  0.20 = 0.30. In my normal table the closest I can find to 0.30 is P(0 < Z < 0.84) = 0.2995 hence (k  27)/7 = 0.84. Solve for k. I hope this helps,  


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