Problema Solution
Find five consecutive odd numbers that have a sum of 65.
Answer provided by our tutors
Every odd number can be written in a form 2k + 1, where k is integer thus for the five consecutive numbers we can write:
2k - 3, 2k - 1, 2k + 1, 3k + 3, 2k + 5, where k is integer
We need to find k so that the sum of the above numbers is 65 that is
(2k - 3) + (2k - 1) + (2k + 1) + (3k + 3) + (2k + 5) = 65
2k - 3 + 2k - 1 + 2k + 1 + 3k + 3 + 2k + 5 = 65
10k + 5 = 65
10k = 65 - 5
10k = 60
k = 60/10
k = 6
The first odd number will be 2k - 3 = 2*6 - 3 = 9
Indeed 9+11+13+15+17 = 65
The five consecutive odd numbers are 9, 11, 13, 15, 17.