Question

list 4 characteristic features of a circuit used in residential building

Answer 1

11. We tend to think of odd numbers as male and even numbers as female.

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This ancient belief was tested by James Wilkie and Galen Bodenhausen of Northwestern University. In his latest book, Alex Bellos writes: "They showed respondents randomly assigned pictures of the faces of young babies, each next to a three-digit number that was either odd-odd-odd or even-even-even, and asked them to guess the baby's sex [...] Respondents were about 10 per cent more likely to say that a baby paired with odd numbers was a boy, than if the same baby was paired with even numbers."

12. If you shuffle a pack of cards properly, chances are that exact order has never been seen before in the whole history of the universe.

Via giphy.com

Proof.

13. Zero is an even number.

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But people take longer to decide whether it's even or odd because it's not as easy for us to mentally categorise.

14. There’s not enough space in the known universe to write out a googolplex on paper.

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According to Carl Sagan in the original Cosmos series. A googolplex is 10 to the power of a googol, or 10 to the power of 10 to the power of 100. This website will write it out for you (or start... it won't ever finish because your computer won't have enough memory).

15. The most popular favourite number is 7.

Flickr: losmininos / Creative Commons

Nearly 3000 people, around 10% of the total asked, chose 7 as their favourite number in an online poll by Alex Bellos. The second most popular was 3.

16. That might be because 7 is “arithmetically unique”.

Flickr: pagedooley / Creative Commons

It's the only number below 10 you can't multiply or divide and keep within group. For example, 5 you can multiply by 2 to get 10 (still within the 1-10 group), 6 and 8 you can divide by 2.

17. 7 also shows up a lot in human culture.

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We have seven deadly sins, and seven wonders of the world. Not to mention colours of the rainbow, pillars of wisdom, seas, dwarves, days in the week...

This might be because when these things came about there were celestial bodies visible in the sky (the Sun, the Moon, Venus, Mercury, Mars, Jupiter and Saturn).

18. The number 4 is considered unlucky in much of Asia.

Flickr: boklm / Creative Commons

That's because the words for "four" in Japanese, Cantonese, Mandarin and Korean (shi, sei, si, sa) sound the same as the words in those languages for death.

19. .999999… = 1

Flickr: andrec / Creative Commons

Here's the proof:

If 10N = 9.9999...
Then N = .9999....
Subtract N from 10N, leaving you with 9N=9.
So then N=1. But we already know that N=.9999... as well. 
So 1=.9999....

20. Cicadas use prime numbers as an evolutionary strategy.

Flickr: oakleyoriginals / Creative Commons

Cicadas incubate underground for long periods of time – 13 or 17 years – before coming out to mate. 13 and 17 are both prime numbers. It's thought cicadas ended up in these prime number life-cycles because it meant they came into contact with predators on more round numbered life-cycles less often.

21. 10! seconds is exactly 6 weeks.

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10! means 10 factorial. 10! = 10 × 9 × 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1 = 3628800 seconds. Which is 42 days, or 6 weeks, exactly.

22. Take any four digit number, follow these steps, and you’ll end up with 6174.

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1. Choose a four digit number (the only condition is that it has at least two different digits).
2. Arrange the digits of the four digit number in descending then ascending order. 
3. Subtract the smaller number from the bigger one. 
4. Repeat.
( It's your that maths facts complete answer starting from 11th point )