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

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

Make eight squares by moving only two matchsticks.
Note- Square can be of different sizes.

Assume there are approximately 5,000,000,000 (5 billion) people on Earth. What would you estimate to be the result, if you multiply together the number of fingers on every person's left hand? (For the purposes of this exercise, thumbs count as fingers, for five fingers per hand.) If you cannot estimate the number then try to guess how long the number would be.

Sherlock Holmes was challenged to make a pre-drawn line smaller without erasing it. He did it in fractions of seconds. How?

In the figure, you can see nine stars. What you have to do is connect all of them by using just four line and without lifting your hand i.e. in a continuous flow.

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

A boy and a girl are sitting on the porch.
"I'm a boy," says the child with black hair.
"I'm a girl," says the child with red hair.
If at least one of them is lying, who is which?

I am a mother. However, I never give birth.

I am a father. However, I never nurse my children.

Wandering is not possible for me, but standing still happens occurs rarely.

Who am I?

You walk into a room that contains a match, a kerosene lamp, a candle and a fireplace. What would you light first?