Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

Why is the Hole below a Lock?

Can you figure out the logic I used to decide the order of the following words:
gun, shoe, spree, door, hive, kicks, heaven, gate, line, den

Rumel, A detective who was mere days from cracking an international smuggling ring has suddenly gone missing. While inspecting his last-known location, you find a note:

710 57735 34 5508 51 7718

Currently, there are 3 suspects: Bill, John, and Todd. Can you break the detective's code and find the criminal's name?

A bank customer had $100 in his account. He then made 6 withdrawals. He kept a record of these withdrawals, and the balance remaining in the account, as follows:

Withdrawals Balance left
$50 $50
$25 $25
$10 $15
$8 $7
$5 $2
$2 $0
----- -----
$100 $99

Why are the Totals not tallying?

If an electric train is travelling south, then which way is the smoke going?

If we tie a Sheep to one peg, a circled grass is been eaten by the Sheep. If we tie the Sheep to two pegs with a circle on its neck, then an eclipse is eaten out of the grass by the Sheep. If we want an eclipse then we put two pegs and then put a rope in between them and the other end of the rope is tied up on the Sheep's neck.

How should we tie the peg and the Sheep so that a square is eaten out from the garden grass? We only have one Sheep rope and the peg and the rings.

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?

Can you find out the remainder when 3^300 is divided by 5?