We represent the weights of the four packages, which increase by 2 pounds each time, as consecutive even numbers starting from x
\(x, x+2, x+4, x+6\)
We translate "The average (arithmetic mean) of four packages is 4 pounds" using the formula for average
\(\frac{x + (x+2) + (x+4) + (x+6)}{4} = 4\)
We multiply both sides by 4 to find the sum of the weights
\(x + (x+2) + (x+4) + (x+6) = 16\)
We combine like terms to simplify the equation
\(4x + 12 = 16\)
We isolate x by subtracting 12 from both sides and then dividing by 4
\(4x = 4\quad\Rightarrow\quad x = 1\)
We list the actual weights by substituting \(x=1\)
\(1, 3, 5, 7\)
We test option A by checking if 9 can be formed as a sum of a combination
\(1 + 3 + 5 = 9\)
We test option B by checking if 10 can be formed
\(3 + 7 = 10\)
We test option C by checking if 12 can be formed
\(5 + 7 = 12\)
We test option D by checking if 13 can be formed
\(1 + 5 + 7 = 13\)
We test option E by checking if 14 can be formed; no two or three weights sum to 14
\(\text{No combination of these weights sums to }14\)
Answer 14 cannot be formed from any combination of the packages, so the answer is E.
Hope this helps!
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