I am white when I am dirty, and black when I am clean. What am I?

1 + 9 + 8 = ?
considering, 28 + 8 + 92 = 10

What does an Island and the letter T have in common?

How can you make the following equation true by drawing only one straight line: 5+5+5=550 ?

If a shopkeeper can only place the weights on one side of the common balance. For example, if he has weights 1 and 3 then he can measure 1, 3 and 4 only. Now the question is how many minimum weights and names of the weights you will need to measure all weights from 1 to 1000? This is a fairly simple problem and very easy to prove also.

A swan sits at the center of a perfectly circular lake. At an edge of the lake stands a ravenous monster waiting to devour the swan. The monster can not enter the water, but it will run around the circumference of the lake to try to catch the swan as soon as it reaches the shore. The monster moves at 4 times the speed of the swan, and it will always move in the direction along the shore that brings it closer to the swan the quickest. Both the swan and the the monster can change directions in an instant.
The swan knows that if it can reach the lake's shore without the monster right on top of it, it can instantly escape into the surrounding forest.

How can the swan successfully escape?

What kind of storm is always in a rush?

Can you find out what is missing?

1 3 5
2 4 ?

Hint: It's not six. Think out of the box.

Manish has to secure 40% marks to pass his B.tech final exams.
He got just 40 marks and failed by 40-marks.

What is the maximum marks?

In a university, a professor gave a set of three problems to the three brilliant students of his class. See the image for the questions.