You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

Can you start the fire using two pieces of wood?

Can you find out which number multiplied by itself will give the output as 12345678987654321?

What question can you never answer yes to?

Find the mistake in the below maths equations

A = 2
A(A-1) = 2(A-1)
A2-A = 2A-2
A2-2A = A-2
A(A-2) = A-2
A = 1

The picture shows the dice results in each couple of throws. If they are actually following a pattern, can you find out the missing one?

Below the four parts have been reorganised. The four partitions are exactly the same in both arrangements. Why is there a hole?

Why do we preferably have round manhole covers and not square ones?

I shave every day, but my beard stays the same. What am I?

A large water tank has two inlet pipes (a large one and a small one) and one outlet pipe. It takes 3 hours to fill the tank with the large inlet pipe. On the other hand, it takes 6 hours to fill the tank with the small inlet pipe. The outlet pipe allows the full tank to be emptied in 9 hours.

What fraction of the tank (initially empty) will be filled in 0.64 hours if all three pipes are in operation? Give your answer to two decimal places (e.g., 0.25, 0.5, or 0.75).