statistic
posted by marie .
Chebyshev's thereon the author's generac produces voltage amounts with a mean of 125.0 volts and a standard deviation of 0.3 volt. using chebyshev's theorem,what do we know about the percentage of voltage amounts that are within 3 standard deviations of the mean? What are the minimum and maximum voltage amounts that are within 3 standard deviations of the mean?

Within 3SD on either side are .4987. Multiply by 200 to get percentage.
You want mean ± 3 SD for min and max. Insert the values and solve.