The average of four consecutive odd numbers is 16. What is the difference between the third and the first number?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 4
Consecutive odd numbers go up by 2 each time. For four such numbers, the average lies half-way between the two middle numbers, so the middle two are the odd numbers on either side of 16.
Middle numbers: 15 and 17
The four numbers: 13, 15, 17, 19
Third \(-\) first \(=17-13=\) 4
Shortcut: the third number is two steps of 2 after the first, so the difference is always \(2\times2=4\); the average is not needed.