10+10 and 11+11 can give you the same answer.

Explain how?

Four people need to cross a rickety bridge at night. Unfortunately, they have only one torch and the bridge is too dangerous to cross without one. The bridge is only strong enough to support two people at a time. Not all people take the same time to cross the bridge. Times for each person: 1 min, 2 mins, 7 mins and 10 mins. What is the shortest time needed for all four of them to cross the bridge?

There is a square of a particular number which when doubled, becomes 7 more than its quarter.

Can you find the number?

Can you make a fire with just a single stick?

A chicken farmer has figured out that a hen and a half can lay an egg and a half in a day and a half. How many hens does the farmer need to produce one dozen eggs in six days?

On a magical land of Mexico , all the animal in the land are rational.

There are 10 tigers and one goat.
Tiger can eat goat but since it's a magical land , the tiger who eats the goat , turns into goat and then can be eaten by the remaining tiger(s).

If we leave them for some time then how many goat and tiger will be there , when we come back ?

I can be cracked, made, told, and played. What am I?

What happened when the wheel was invented?

Which alphabet letter is a question?

I am a white box having no key or lid.
Yet there is a golden treasure inside it.

What Am I?