What number does the below three word/phrase identify and why?
1. Deck
2. Year
3. Singing in the Rain

In a school, 280 students studied chemistry, 254 students studied physics and 280 students studied biology.

97 students studied chemistry as well as physics, 138 students studied physics as well as biology and 152 students studied chemistry as well as biology.

73 students studied all the three branches.

Can you find out the total number of students?

Can you count the number of quadrilaterals in the picture below?

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

A train full of passengers goes through a tunnel. When the train comes out from the other end, there is no single person on the train.

How did it happen?

I had an infinite supply of water and 5 litres and 3 litres jars.

How would you measure exactly 4 litres in the least number of steps?

The first box has two white balls. The second box has two black balls. The third box has a white and a black ball.

Boxes are labeled but all labels are wrong!

You are allowed to open one box, pick one ball at random, see its colour and put it back into the box, without seeing the colour of the other ball.

How many such operations are necessary to correctly label the boxes?

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

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?

Many have heard it, but nobody has ever seen it, and it will not speak back until spoken to. What is it?