csat-suneung 2006 Q28

csat-suneung · South-Korea · csat__math-humanities 4 marks Combinations & Selection Selection with Arithmetic or Divisibility Conditions
When selecting two different odd numbers from the odd numbers from 1 to 30, how many cases are there where the sum of the two numbers is a multiple of 3? [4 points]
(1) 43
(2) 41
(3) 39
(4) 37
(5) 35
When selecting two different odd numbers from the odd numbers from 1 to 30, how many cases are there where the sum of the two numbers is a multiple of 3? [4 points]\\
(1) 43\\
(2) 41\\
(3) 39\\
(4) 37\\
(5) 35