Do Americans work more than the French? American adults work on average 43.5 hours per week with a standard deviation of 4.6 hours. French adults work an average of 36 hours per week with a standard deviation of 5.1 hours. A random sample of 110 Americans and 135 French adults were selected and surveyed about their work time. What is the probability that the sample mean for French is greater than that of the Americans?

With a probability of 0.85 the difference in average hours per week worked (American - French) is above what number?

if a = 1,   and b = 2, then the answer is 47.99999999. if you round that to the nearest whole number, the answer is 48.

solution:

the given function is ,

      =

the three roots of this quadratic function is , 0 ,8 and 10.all the roots are real and rational.

if a quadratic equation is of the form ,

sum of the roots = a + b +c= 0+8+10=18=  

product of roots taken two at a time = a b + b c+ c a = 0+80+0=80 =  

product of roots = a b c = 0=  

there are 11 doors in a hall starting from 0 to 11.the entry in the hall is permitted through gate number 0 and exit is allowed through only gate number 8 and 10.so, three roots(0,8,10) of quadratic function is given by entry and exit route of this hall.