What happened when the wheel was invented?

Arrange the numbers 1, 2, 3, 4, 5, 6, 7, 8 and 9 above and below the division line in a manner that the thus formed fractions equal to 1/3.

(You can use one number only once)

If,

6 / 7 = 2
3 / 9 = 7
8 / 2 = 6

Then

4 / 5 = ?

Find the next number in the series below

21 32 54 87 131 ?

I am the black child of a white father, a wingless bird, flying even to the clouds of heaven. I give birth to tears of mourning in pupils that meet me, even though there is no cause for grief, and at once on my birth, I am dissolved into air. What am I?

Replace each alphabet with the number (1-9) to make the below equation correct.

AB * C = DE - F = GH / I

A large container is kept in open under the rain. Every passing hour, the water collected inside the container becomes double what it was.

In ten hours, the container is filled completely. Can you calculate how long would it have taken to be filled in half?

What demands an answer, but asks no questions

What is black when you buy it, red when you use it, and gray when you throw it away?

Aman has 1.15 rupees in his pocket. There are a total of 6 coins in his pocket.

When his friend asked him for a change, he could not give change for a rupee and five paisa.

Can you tell which coins he has?