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?
Carol is sending out invitations to 10 friends, so she needs 10 invitations in total. 

Each package of invitations has 2 invitations in it, so she would need 5 packages of invitations to get 10 invitations in total. 

Therefore, the answer (numeric) is: 

5