Why manhole covers are round shaped?

For some one who doesn’t know what is Manhole cover, then, it’s a covering over the manholes, which can be removed and fitted easily. Any one could see them wherever the underground drainage passes near by your house or road.
Now the question is, why these manhole covers are round shaped!!! When I googled the shape of manhole covers, its mostly in round in shape. Also have got some images of the Rectangle and triangle shaped covers! But mostly in round shaped. There are many theories revolving around! Lets see some glimpses of that!
1) Manhole covers are round because the manholes are round.
2) Only round manhole covers will not fall in to the man hole
3)Heavy, round manhole covers are easier for one person to move by rolling.
4) You also don't have to "align" a manhole cover to its hole. Any orientation of the cover will do this.
5) Round manhole covers are easier to manufacture.§ Animals dig round holes, so it natural for humans too to do the same.
6) If any other shapes of sharp corners are followed then the sharp corners will pop up and have a possibility of hurting the car tires and humans!
7) The tunnels are pipes so its easier to go with the whole theme or circularity
8) If you stress test an a circle you will find that the circle dissipates the stress more evently at all points.
8) When you heat metals, they expand. Assume that you choose any shape other than circle, when they expand you can not know which parts becomes longer than other parts. But with circles they expand (almost) uniformly. So even with expanding they are easier to remove and put back in. So when they expand they do not get stuck.
9) Circular man holes are easy to dig. Hence covers are also round.

So this means manholes are one of the few things in the universe that are absolutely goof proof. Now it time to know one more fact about these manholes cover. This question in one which was asked in Microsoft’s Interview. So don’t try to ignore. It may also fetch u a job in some other company too!! Good Luck friends!!!

ATM Machine Facts

1. ATM customers spend an average of 20 to 25% more than non-ATM customers.
2. 60% of Americans ages 25-34 and 51% ages 25-49 use ATM machines 8 times a month, withdrawing an average of $55.00 per transaction.
3. In 1994, there were 8.3 billion ATM transactions in the United States.
4. Bank ATMs average 6,400 transactions per month.
5. The most popular day for ATM usage is Friday.
6. Among people that use both credit and debit cards, debit cards are used most often. 5.9 times per month versus 5.1 times per month.
7. Independent studies show that cash retention among large retailers is 30-33%. Retention among smaller retailers is 35-40%.
8. Nightclubs are seeing 70-80% of the dispensed cash staying at the club.
9. Retail location ATM machines that dispense $20.00 bills increase store sales by over 8%.
10. Luther George Simjian was believed to be the inventor of ATM machines by .ATMmachines.com
11. There are over 1.2 million ATMs installed worldwide, according to estimates by Retail Banking Research Ltd.
12. Approximately every 5 minutes a new ATM is installed.
13. According to Thomson Media’s ATM and Debit News, the number of ATMs currently deployed in the U.S. alone is about 371,000.
14. Various industry bodies help to self-regulate the ATM industry including banking associations, electronic funds transfer associations, network associations and the internationally active ATM Industry Association (ATMIA).
15. The ATM is one of the most important technological inventions of the second half of the twentieth century, helping to create the 24 X 7 open convenience demanded by the consumer society.
16. The ATM provides millions of cardholders around the world with convenient 24 X 7 all hours’ access to their own banked cash near to where they live, work and shop.
17. ATMs have made banking more convenient today than ever before: with the touch of a few buttons, cardholders can withdraw cash, make deposits, top up air time, pay bills and transfer funds.
18. The industry does care about the security of cardholders and has formed a Global ATM Security Alliance (GASA) to combine global security resources to stamp out crime and fraud connected to ATMs.
19. Customer security is a key consideration when choosing sites for ATMs.
20. Shared ATM Networks came to existence only by early 80’s.
21. ATM Stands for Automated Teller Machines. Initially they are used instead for Trained Human tellers.
22. NCR, Diebold, Fujitsu, Triton are most common ATM machine models.
23. Using PIN number was the most familiar way of authenticating the user in an ATM machines. But many alternate ways like, Retina Scan method, facial recognition, Finger print authentication and many other things were also in research.
24. In order to with access our accounts using ATMs we have to own a Credit card or a Debit card from respective bank.Apart from withdrawing the money, we can check account balance, transfer money, Change PIN, deposit funds, Mini Statements.