Question

Ann, Mara, Jenny , Tina, and Sue are sisters. Two of the five sisters must help their father

Answer 1

Imagine taking from the group of five sisters to fill two slots. To fill the first slot, there are 5 different sisters that could do it. To fill the second slot, there would only be four left to fill the slot since one is in the first slot.

Therefore, there are 5 * 4, or 20 ways the girls can fill 2 slots. Hope this helps! :)