Riddle: Two mothers and two daughters go shopping. They have $21, which they split equally between them. How can this be possible?
The answer of this riddle is that there are only three people. The only purpose of this riddle is to confuse you. When you hear that two mothers and two daughters are going shopping, you might think there are 4 people in total. For this reason, it may seem impossible for you to share $21 equally.
But imagine that these people are a grandmother, a mother and a daughter. Grandmother is also a mother. Mother is also a daughter. Thus, 2 mothers and 2 daughters are 3 people in total and they each get $7 exactly.
Answer: There are only three people. One of the mothers is a daughter also, because there is a grandmother, a mother and a daughter! They each get $7 exactly.