I’m light as a feather, yet the strongest person can’t hold me for five minutes. What am I?

Below, you can see three complete equations and one incomplete. Based on the three complete ones, can you complete the incomplete one?

5 $ 4 $ 3 $ 9 = 4215
6 $ 9 $ 2 $ 6 = 3816
4 $ 7 $ 3 $ 3 = 1122
7 $ 2 $ 7 $ 4 = ____

Two boys wish to cross a river. The only way to get to the other side is by boat, but that boat can only take one boy at a time. The boat cannot return on its own, there are no ropes or similar tricks, yet both boys manage to cross using the boat.

How?

Make the seating arrangement of 10 children in such a way that there are 5 rows with 4 children in each row.

Find the last number in the series below:

voN luJ yaM raM ---

Why is it against the law for a man living in Delhi to be buried in Mumbai?

I am a type of word that is spelt incorrectly or used differently, on purpose for humour. What am I?
Hint 1: You can find me in a joke.
Hint 2: I am a play on words.

In the image given, you can find several triangles. Can you count them all?

They came out at night, without being called.
They lost at day, without being stolen.
Who are they?

A girl rode into a tourist spot out of the city on Thursday. She loved the place and decided to stay for a few days. She stayed for four days and then she left for back home on Thursday.

How can this be possible?