6. The probability distribution for both values of a random variable X is given in the table below.
Given that the expected value of X is 20, what is the value of k ?
A. 6
B. 8
C. 16
D. 24
E. 28
7. For what values of x, if any, is −⎪−x⎪ < 0 true?
F. No real values of x
G. Only negative values of x
H. Only positive values of x
J. All real values of x except 0
K. All real values of x
8. Two functions, f and g, are defined over all real numbers by f(x) = 2x − 1 and g(x) = 3×2 − 7. What is g(f(5x))?
9. An investment doubles in worth every 7 years. The worth of this investment was $24,000 exactly 21 years after the investment was made. The worth of the investment exactly 8 years after the investment was made was between:
F. $0 and $3,000
G. $3,000 and $6,000
H. $6,000 and $9,000
J. $9,000 and $12,000
K. $12,000 and $24,000
10. You want to list all the positive two-digit numbers for which the units digit is larger than the tens digit and for which the sum of the digits is 12. How many two-digit numbers should be on your list?
A. 1
B. 3
C. 5
D. 6
E. 7