Name a key which is hardest to turn.

There are people and strange monkeys on this island, and you can not tell who is who (Edit: until you understand what they said - see below). They speak either only the truth or only lies.
Who are the following two guys?
A: B is a lying monkey. I am human.
B: A is telling the truth.

Why is 6 afraid of 7?

What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

The Puzzle: A girl, a boy, and a dog start walking down a road.

They start at the same time, from the same point, in the same direction.

The boy walks at 5 km/h, the girl at 6 km/h.

The dog runs from boy to girl and back again with a constant speed of 10 km/h. The dog does not slow down on the turn.
How far does the dog travel in 1 hour?

You are mixing a mixture of cement and Sand with five gallons of water. You have a garden hose giving you all the water you need. The problem is that you only have a four-gallon bucket and a seven-gallon bucket and neither has graduation marks. Find a method to measure five gallons.

O_er_t_o_

Complete the missing letters of the given word.

Replace the letters of words with a number so that the below equation holds true

BASE +
BALL
---------
GAMES
----------

Find the Goldfish below the given Image.

A finger goes in me. You fiddle with me when you're bored. The best man always has me first. What am I?