Gerald bought 3 shirts for 8.40 each, 2 shirts for 12.89 each, and one shirt for 18.90. What was the average cost of the shirts?
2 answers:
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Notice that the pattern is "previous term plus 2". This is an arithmetic sequence where the difference (d) equals +2
= a₁ + d(n - 1) ; where a₁ is the first term, d is the difference, and n is the term.
f(n) = 1 + 2(n - 1)
f(n) = 1 + 2n - 2
f(n) = 2n - 1
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f(10) = 2(10) - 1
f(10) = 20 - 1
f(10) = 19