For the given five values, 17, 25, 21, 35, 43, the three-year moving averages are:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 21, 27, 33
A three-year moving average is the mean of each set of three consecutive values, moving forward one value at a time:
\( \displaystyle \frac{17+25+21}{3}=\frac{63}{3}=21 \)
\( \displaystyle \frac{25+21+35}{3}=\frac{81}{3}=27 \)
\( \displaystyle \frac{21+35+43}{3}=\frac{99}{3}=33 \)
So the moving averages are 21, 27, 33.
Shortcut: Use differences: each new three-year total = previous total − value dropped + value added. From 63: 63 − 17 + 35 = 81, then 81 − 25 + 43 = 99.