If eleven plus two equals one, what does nine plus five equal?

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

Prove that twice of ten is the same as twice of eleven.

Most people think of me as money. But when they find me in the water, they won’t get any money out of me. What am I?

Doctor Alex and a bus driver John are both in love with the same woman named Olivia. The bus driver need to go for a long trip of 10 days, Before he left he gave Olivia 10 apples.

Here is a conversation between a couple who both are software professionals.

Husband: Hey! What is your date of birth?
Wife Replied Angrily: It is 591062400
Husband after doing some calculations replied, "Got It".

What is the DOB of the wife?

Can you solve the tricky chess rebus puzzle below by ciphering the hidden meaning?

In a science lab, a petri dish hosts a healthy colony of yeast for an experiment. Now every minute, all the yeast cells divide into two. At noon, there was just a single cell of yeast and at 1:22, the Petri dish was half full. Can you calculate when the dish will be full of yeast?

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

They are the five precious gems of an everyday sort and all can be found on a Tennis Court. Who are they?