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

Analyze and find the missing item in the sequence:
16, 06, 68, 88, __, 98

There are 2 people near the river and both of them want to get on the other side. The boat can only take one of them. But they got across.
How?

Find the next number in the series?
2, 12, 36, 80, 150, 252, 392, _ ?

Take away the whole and some still remain. What is it?

I have two coins.
* One of the coins is a faulty coin having a tail on both sides of it.
* The other coin is a perfect coin (heads on side and tail on other).

I blindfold myself and pick a coin and put the coin on the table. The face of the coin towards the sky is the tail.

What is the probability that another side is also tail?

Here is what you have to do. You have to throw a ball as hard as you can but it must return back to you even if it does not bounce at anything. Also, you have nothing attached to the ball. There is no one on the other end to catch that ball and throw it back at you.

How will you do it?

If,

A = 1

B = 2

C = 3

...

...

Z = 26.

Based on above rule, you need to find an eleven letter word whose letter sum is equal to 52.

John and Jacob are twin brothers. One of them is a liar whereas the other one is a truth-teller.

I called their home number and one of them picked up.
I asked. 'Does John lie?' The person replied with a yes.

Whom did I talk with, John or Jacob?

I have branches, but no fruit, trunk or leaves. What am I?