Name a key which is hardest to turn.

What number comes next in the series?

5 15 5 18 5 24 14 20 _

I want to fill my bucket using both cold and hot water.
I have two taps for both cold and hot water. The hot water tap fills the bucket in exact 6 hours and the cold water tap fills the bucket in exact 4 hours.
I turn both of them simultaneously but I forgot to turn off another tap which removes the water out of the bucket. This tap can empty the bucket in 12 hours.

How Long will it take to fill the bucket?

Below the four parts have been reorganised. The four partitions are exactly the same in both arrangements. Why is there a hole?

People put me on the table and cut me but do not eat me. What am I?

What is the riddle which can be asked all day with a different correct answer each time.

How many times can you subtract the number 5 from 25?

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

Begin with a word, five letters to my name,
Remove the first and last but I am the same
Take out my middle and still, I remain.
What word am I?

What can go up a chimney down, but can’t go down a chimney up?