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 is the centre of gravity?

A man dies of old age on his 25 birthday. How is this possible?

Can you make numbers like 24, using numbers 3,3,7 & 7 with any arithmetic operator?

A mile-long train is moving at sixty miles an hour when it reaches a mile-long tunnel. How long does it take the entire train to pass through the tunnel?

You can take four of the five letters out of this word, but the pronunciation never changes. What is the word?

Forwards I am heavy, backward I am not. What am I?

The square root of number 121 is "11". What is the square root of the number "12345678987654321."?

The pound is not a finish.

We are sharing a few instructions below, which you have to use in any suitable order to modify the above sentence such that the end sentence is a scientific fact.

- Eliminate a letter and supplement another in its place.
- Take away one word.
- Remove one letter from one word.
- Get rid of two letters from one word.
- Swap a word with its antonym.

What is the largest number you can write with just 3 digits?