Why is 6 afraid of 7?

The king of Octopuses has servants who have six, seven or eight legs. The distinguishing characteristics of the servants is that the one with seven legs always lie but the one with either six or eight legs speak the truth always.

One day, four servants meet and converse:

The black one says, 'We have 28 legs altogether.'

The green one says, 'We have 27 legs altogether.'

The yellow one says, 'We have 26 legs altogether.'

The red one says, 'We have 25 legs altogether.'


Can you identify the colour of the servant who is speaking the truth?

A man and a dog were going down the street. The man rode, yet walked. What was the dog’s name?

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.

The centre of the third figure is empty. What digit should fit inside?

How many times can you subtract the number 5 from 25?

In the given figure, you can see that four match sticks are used to form a square. Can you form five squares by using six matches?

Considering the below equation:

V + II - VI = 10
IV - X + VIII = 20
IV - VII + VI = 30

Then, I + II + III = ?

Place the numbers from 1 to 9 in the circles in a manner that each side of the triangle sums up to 17.

Can you find out the missing number?

? 4 5 3 5

9 5 7 10 3