What always comes into a house through the keyhole?

What does below chemistry rebus means?

Today, I celebrated my 32nd birthday but I was born in 1972.
How is this possible?

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

Our product and our sum always give the same answer. Who are we?

Identify the next two numbers in this series.

101, 112, 131, 415, 161, 718, ???, ???

I am an odd number. Take away a letter and I become even. What number am I?

Complete the series by replacing "?" with the correct number.

ST ND RD TH '?'

How many words can a quill made with the feather of a pigeon write with a 100ml bottle of black ink?

John is a strange liar.

He lies on six days of the week, but on the seventh day, he always tells the truth.

He made the following statements on three successive days:

Day 1: "I lie on Monday and Tuesday."
Day 2: "Today, it"s Thursday, Saturday, or Sunday."
Day 3: "I lie on Wednesday and Friday."

On which day does John tell the truth?