I never stop running even when I standstill. If I am formed by joining two identical bodies together, can you guess who I am?

Using Only Five 5's and any mathematical operator make sum as 37

A word I know,
Six letters contain,
Subtract just one,
And twelve is what remains.

Find the next number in the series

12, 20, 40, 72, 116, 172 ?

John can place six large boxes or nine small boxes into a carton.

Can you find out in how many cartons can he place sixty-six boxes in total?

How many words can a pen with half refill write?

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?

I cry without having a voice.
I fly without having wings.
I bite without having teeth.
I whisper without a mouth.

Who am I?

A train full of passengers goes through a tunnel. When the train comes out from the other end, there is no single person on the train.

How did it happen?

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