What has no start, end, or centre?

Where do you go to learn how to make ice cream?

When is the top of a mountain similar to a savings account?

It belongs to you, but other people use it more than you do. What is it?

When 99 is considered higher than 100?

If,
9 * 8 * 7 = 65
8 * 7 * 6 = 50
7 * 6 * 5 = 37

Find
6 * 5 * 4 = ?

What is the four-digit number in which the first digit is one-third the second, the third is the sum of the first two, and the last is three times the second?

What is so fragile that saying its name breaks it?

A river should be crossed by a father, a mother and their two sons and two daughters.
There are some rules that should be followed while crossing the river. There can be only two people in the raft while crossing. The daughters cannot be with their father unless there is the presence of the mother. The sons cannot be with their mothers unless the father is present. Unless the guard is on the board, the criminals cannot be with any of the family members. Only the adults like the father, the guard, and the mother knows to use the raft.

How will they cross the river?

What number comes next in the series?

5 15 5 18 5 24 14 20 _