Let $a, b, c, d, e, f, g$ be seven consecutive even numbers and $j, k, l, m, n$ be five consecutive odd numbers. What is the average of all numbers?
Solution
✅ Correct Option: 2
When numbers are equally spaced, their average is simply the middle number. | Group | How many | Middle term | Sum | |---|---|---|---| | Even numbers $a$ to $g$ | 7 | $d$ | $7d$ | | Odd numbers $j$ to $n$ | 5 | $l$ | $5l$ | There are $7+5=12$ numbers in all. $\text{Average}=\dfrac{7d+5l}{12}=\dfrac{5l+7d}{12}$