Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

You have a three-gallon and a five-gallon measuring device. You wish to measure out four gallons.

A man is approaching a broad and barren land. He has a package with him. If somehow, he is unable to open the package before reaching the land, he will die.

Can you guess what is present in the package?

If eleven plus two equals one, what does nine plus five equal?

Pronounced as one letter,
And written with three,
Two letters there are,
And two only in me.
I am double, I am single,
I am black blue and grey,
I am read from both ends,
And the same either way.

What occurs twice in a week, once in a year but never in a day?

100 prisoners are stuck in the prison in solitary cells. The warden of the prison got bored one day and offered them a challenge. He will put one prisoner per day, selected at random (a prisoner can be selected more than once), into a special room with a light bulb and a switch which controls the bulb. No other prisoners can see or control the light bulb. The prisoner in the special room can either turn on the bulb, turn off the bulb or do nothing. On any day, the prisoners can stop this process and say "Every prisoner has been in the special room at least once". If that happens to be true, all the prisoners will be set free. If it is false, then all the prisoners will be executed. The prisoners are given some time to discuss and figure out a solution. How do they ensure they all go free?

How can I get the answer 24 by only using the numbers 8,8,3,3?

You can use the main signs add, subtract multiply and divide.

Count the Triangle in the figure given below:

Using eight eights and addition only, can you make 1000?