Carol was sending out birthday invitations to 10 friends. If each package of invitations she bought had 2 invitations in it how many packs does she need so that no friend gets left out?
Let's denote the number of friends by n. Then we need n/2 packs of invitations. 

However, we need to take into account that we need to round up. 

Therefore the answer (numeric) is: 

n/2 = 10/2 = 5