The following table relates the number of objects f corresponding to a certain size x. What is the average size of an object?
(begin{array}{cc} f & 1 & 2 & 3 & 4 & 5 \ hline x & 1 & 2 & 4 & 8 & 16end{array})
(begin{array}{cc} f & 1 & 2 & 3 & 4 & 5 \ hline x & 1 & 2 & 4 & 8 & 16end{array})

A.
(frac{31}{15}) 
B.
(frac{31}{5}) 
C.
(frac{129}{5}) 
D.
(frac{43}{5}) 
E.
(frac{16}{5})
Correct Answer: Option D
Explanation
F = 1, 2, 3, 4, 5
x = 1, 2, 4, 8, 16
fx = 1, 4, 12, 32, 80, 3f = 15
(average size) = (frac{sum fx}{sum f})
= (frac{129}{15})
= (frac{43}{5})