Answers

1.

Two mathematicians meet, who hadn't seen for a long time.

-How many children do you have?

-Three.

-How old are your children?

-If we multiply their age, we will get 36.

-I can't give an answer.

-If we add up their age, we will get the number of your house.

-This data is not sufficient.

Second mathematician thought it over and said:

-My eldest son is redhead.

After that first mahemician gave an answer.

2.

In the 12-storey house there is an elevator. On the first floor there are only 2 people, from the floor to the floor the number of residents is doubled. On which floor in this house is most often pressed the button to call the elevator?

Here the answers to the riddles:

1. 2-2-9
2. First floor