What goes up but never comes down?

What's the next in the series?

H, Be, F, S, Mn, Kr, In, Gd, Tl, ?

Use the digits from 1 up to 9 and make 100.

Follow the rules.
=> Each digit should be used only once.
=> You can only use addition.
=> For making a number, two single digits can be combined (for example, 4 and 2 can be combined to form 42 or 24)
=> A fraction can also be made by combining the two single digits (for example, 4 and 2 can be combined to form 4/2 or 2/4)

Question: how can we do this?

See the given image carefully. What you have to do is move the blue checkers in the position of the black checkers and vice versa. You are only allowed to move the checker to an adjacent empty space. Do it in the least possible moves.

You need to move three matchsticks to form three squares. Can you do it?

I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

Can you calculate the probability of getting a sum of six when a dice is thrown twice?

Can you place three balls such that the equation shown in the picture holds true?

What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

Find the missing letter in the last circle logically in the given below picture.