What has many keys but can’t open a single lock?

Three people are in a room. Ronni looks at the Nile. The Nile looks at Senthil. Ronni is married but Senthil is not married. At any point, is a married person looking at an unmarried person? Yes, No or Cannot be determined.

You have two strings whose only known property is that when you light one end of either string it takes exactly one hour to burn. The rate at which the strings will burn is completely random and each string is different.

How do you measure 45 minutes?

A train leaves from point A for point B at 80 mph. After half an hour, another train leaves from point B for point A at 60 mph.

Which of the trains will be farther from point A when they meet ?

During which month do people sleep the least?

I know a ten-letter word in the English language which can be typed using only the top rows of the computer keyboard.

Can you find the key in the picture below?

The product of three consecutive numbers is 7980.
Then the sum of these consecutive numbers would be?

A word I know,
Six letters contain,
Subtract just one,
And twelve is what remains.

Using the clues below, what four numbers am I thinking of?

The sum of all the numbers is 31.
One number is odd.
The highest number minus the lowest number is 7.
If you subtract the middle two numbers, it equals two.
There are no duplicate numbers.