What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

I want to fill my bucket using both cold and hot water.
I have two taps for both cold and hot water. The hot water tap fills the bucket in exact 6 hours and the cold water tap fills the bucket in exact 4 hours.
I turn both of them simultaneously but I forgot to turn off another tap which removes the water out of the bucket. This tap can empty the bucket in 12 hours.

How Long will it take to fill the bucket?

Transform the word THINK into BRAIN while changing only one letter at a time in a manner that each of the word in the process is a real word!!!

A pond had 60 fish, out of which, all but 20 died.
How many fishes are now present in that pond?

Two boys were admitted to a school. When the headmaster asks them about their parents, they tell him that they have same parents (father and mother). On further inquiry, it turns out that they both share the same date for their birthday.

"Are you twins," ask the headmaster.
"No," replies the boys.

Is it possible?

You need to arrange three 7 and mathematical symbols to form number 1?

John’s parents have three sons: Snap, Crackle, and what’s the name of the third son?

There are two candles. Both will only burn exactly for an hour. How will you use these two candles to measure forty-five minutes?

Using the clues below, what four numbers am I thinking of?

The sum of all the numbers is 31.
One number is odd.
The highest number minus the lowest number is 7.
If you subtract the middle two numbers, it equals two.
There are no duplicate numbers.

I am lying and I always lie. Tell me whether I am lying or telling the truth.