Final answer:
The riddle involves understanding family relationships. There are only three people: a grandmother (who is also a mother), a mother (who is also a daughter), and a daughter, so they bought three ice-creams in total.
Step-by-step explanation:
The question asks how many ice-creams were bought by a grandmother, two mothers, and two daughters. This may initially seem like a tricky question, but it is a simple problem once you understand the relationships between the family members. Here, the grandmother is also the mother of the mother, and that mother is also the mother of the daughter. This means that there are actually only three people involved: the grandmother (who is also a mother), the mother (who is also a daughter), and the daughter. Therefore, they would buy three ice-creams in total.