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

Which number should replace the question mark?

Replace the question mark with the correct number, given the pair of numbers exhibits a similar relationship?

? : 3839 :: 11 : 1209

There is a square of a particular number which when doubled, becomes 7 more than its quarter.

Can you find the number?

I organized a small get together at my home.
In the party , i have a barrel with some whiskey in it.

Suddenly Guest 1 say 'I bet this barrel of whiskey is more than half full'.
'No, it's less than half full' Guest 2 replied.

I don't have any measuring instrument and without removing whiskey from it , how can i determine which of the guest is right ?

When you say goodbye, I am what you need to tie.
I come as a couple and go wherever you run.
Who am I?

If,

Akriti = 631
Levis = 521
Sroti = 521
Aneel = 533
Then,
Sunil =?

They are the five precious gems of an everyday sort and all can be found on a Tennis Court. Who are they?

You see me once in June, twice in November, and not at all in May. What am I?

Complete the series by replacing "?" with the correct number.

ST ND RD TH '?'