Doubt in Quiz of Maths

#1

Can you please help me in this question:

From the set of numbers s={1, 2, 3, 4}, how many minimum numbers must be selected to guarantee that at least one pair of these numbers has a sum equal to 7?

#2

@mgfags,
Let’s check the answer from subset size(=s) 1 to n,
For s=1, You can choose no pair,
For s=2, You can choose {1,2} which does not have and pair sum = 7,
For s=3,You can choose {1,2,3} which does not have pair sum = 7,
Thus answer is s=4.