# Find even sum from a given set

For a set that contains $$=\{1,2,3,4,5,6,7,8,9\}$$

How many times minimally do I have to randomly pick a number from the set to ensure the sum is even?

• any thought about the question? – Siong Thye Goh Nov 1 '18 at 15:12
• Hint: for a bad scenario, you must first draw an odd number and thereafter draw even numbers. – lulu Nov 1 '18 at 15:17
• Is there any general formula to use? – user10456099 Nov 1 '18 at 15:20
• Please show some efforts. If you can solve the problem in this case, I think you will see how to do it in general. – lulu Nov 1 '18 at 15:21
• Do refer to my working below,i am not sure if it is the correct answer. – user10456099 Nov 1 '18 at 17:26

Remember: $$even+even=even$$ $$odd+odd=even$$ $$odd+even=odd$$
If you want to ensure the sum is even, you have to find the maximum number of picks. $$odd+even+even+even+even=odd$$ is the maximum number of picks to get odd.