What four weights can be used to balance from 1 to 30 pounds?

Outside a tattoo artist's shop, there was a signboard which read 'I make tattoos on only them who do not tattoo themselves'.

Reading it what do you think, does the tattoo artist tattoo himself?

Can you replace the question mark with the correct number in the below table sequence?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

Which Number is the odd one out?

A) 7145
B) 2716
C) 5321
D) 4135

Is the statement valid that it does not matter how much older a sibling is, eventually the younger one will be half as old as the older one?

John was piloting a plane behind a car but was never able to overtake it. Why?

Until it is measured, not known. Yet how you miss it when it has gone. What is it?

John was writing his first book. After saving the document, he locked his laptop with a password and mentioned some phrases for the hint box.

A friend of his tried opening his laptop but found out that it was password protected. Following is the hint that appeared.
1 mobile 3 books 2 roars 1 night 4 balls 2 lighters 1 ghost 1 hat 3 watches.

Can you help him in cracking the password?

I know a nine-letter word having only one vowel.
Do you ?