document.write( "Question 358978: I'm not sure if this is the right section, but this question is about the normal distribution:
\n" ); document.write( "Tony is training for the athletic sports. He has found that 70% of the times he records are less than 56.3 seconds and 20% are less than 52.3 seconds. If the times he records are normally distributed then what are mean and the standard deviation of his times?
\n" ); document.write( "Thanks in advance. \n" ); document.write( "

Algebra.Com's Answer #256164 by robertb(5830) $\"\"$ $\"About$

You can put this solution on YOUR website!
Reading off from a standard normal table, and using the formula $\"Z+=+%28X+-+mu%29%2Fsigma\"$ , we get the system
\n" ); document.write( " $\"matrix%282%2C1%2C+-0.845+=+%2852.3+-+mu%29%2Fsigma%2C+0.525+=+%2856.3+-+mu%29%2Fsigma%29\"$ .
\n" ); document.write( "Solving for $\"mu\"$ and $\"sigma\"$ , we should get
\n" ); document.write( " $\"mu+=+54.767\"$ , and $\"sigma+=+2.92\"$ . \n" ); document.write( "

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