For the given five values, 13, 17, 21, 25, 35, the three years moving averages are:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 17, 21, 27
A three-yearly moving average is the mean of each set of three consecutive values, moving one value at a time. Five values give 5 − 3 + 1 = 3 averages.
\( \displaystyle \frac{13+17+21}{3}=\frac{51}{3}=17 \)
\( \displaystyle \frac{17+21+25}{3}=\frac{63}{3}=21 \)
\( \displaystyle \frac{21+25+35}{3}=\frac{81}{3}=27 \)
So the moving averages are 17, 21, 27.
Shortcut: The second average is the mean of 17, 21 and 25, which lie in steps of 4, so it is the middle value 21. Only Option (2) has 21 in the second place.