Respuesta :
Subtracting their means, it is found that the mean of D is of 30.
- When two variables are subtracted, the mean is the subtraction of the means, while the standard deviation is the square root of the sum of the variances.
In this problem, the means of the variables are:
[tex]\mu_B = 610, \mu_A = 640[/tex]
Since D = A - B, the mean of D is:
[tex]\mu_D = \mu_A - \mu_B = 640 - 610 = 30[/tex]
The mean of D is of 30.
A similar problem is given at https://brainly.com/question/16371181