document.write( "Question 439886: A light bulb has an average life of 500 hours with a std. deviation of 100 hours. This can be approx. by a normal distr. curve. An amusement park buys and installs 10,000 of such bulbs. Find the total number than can be expected to last for:\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "a) Less than 500 hours
\n" ); document.write( "b)more than 440 hours \n" ); document.write( "
Algebra.Com's Answer #304121 by ewatrrr(24785)\"\" \"About 
You can put this solution on YOUR website!
 
\n" );
document.write( "Hi
\n" );
document.write( "A light bulb has an average life of 500 hours with a SD = 100 hours.
\n" );
document.write( "amusement park buys and installs 10,000 of such bulbs.
\n" );
document.write( " Number lasting <500hr: 50% of them OR 5,000
\n" );
document.write( " Number lasting more than 440 hours = .7557*10,000 = 7,557 
\n" );
document.write( "*Note: \"z+=+blue%28x+-+mu%29%2Fblue%28sigma%29\"
\n" );
document.write( "   z = (440-500)/100 = -.6
\n" );
document.write( " P(z > -.6) = 1 -  NORMSDIST(-.6)= 1 - .2743 = .7557  OR 75.57%
\n" );
document.write( " \n" );
document.write( "
\n" );