Question 624015
  <pre><font face = "Tohoma" size = 3 color = "indigo"><b> 
Hi
for at least 210, using 209.5 is the correct spproach
 z = (209.5 - 184)/25 = .4636 which results in  .6786  or 67.86% to the left
Note: we know as 210 >184 that this P has to be greater than 50% for 
Also as to Your P(x&#8805;210) = {{{highlight(.3214)}}} Note (1-.3214) = .6786
_____________________________________________________________________________
Important to Understand z -values as they relate to the Standard Normal curve:
Below:  z = 0, z = ± 1, z= ±2 , z= ±3 are plotted.  
Note: z = 0 (x value the mean) 50% of the area under the curve is to the left and %50 to the right
{{{drawing(400,200,-5,5,-.5,1.5, graph(400,200,-5,5,-.5,1.5, exp(-x^2/2)), green(line(1,0,1,exp(-1^2/2)),line(-1,0,-1,exp(-1^2/2))),green(line(2,0,2,exp(-2^2/2)),line(-2,0,-2,exp(-2^2/2))),green(line(3,0,3,exp(-3^2/2)),line(-3,0,-3,exp(-3^2/2))),green(line( 0,0, 0,exp(0^2/2))),locate(4.8,-.01,z),locate(4.8,.2,z))}}}