Absolutely brutal maths quiz

[rockchick]

I'm almost willing to offer a cash prize for this one.

Maths quiz question I came across today: Any takers?

What is the next number in the sequence? 10001, 122, 101, 32, 25, 23, 21 ...

Answers:

a) 20
b) 18
c) 15

...if you think you know the answer, please explain what your reasoning is.

[changilass]

18. This was a tough one. 18 is 17 in base 9. They are the prime number 17 in different bases.10001 is binary for 17=1x16+0x8+0x4+0x2+1x1. 122 is 17 in base 3. 17=1x9+2x3+2x1 101 is 17 in base 4. 17=1x16+0x4+1x1.


Google is great

[Julia]

The answer is 18, as Changi said they are all the prime number 17 in different bases :eek:

[joxville]

42. According to the Hitchhikers Guide To The Galaxy.

[rockchick]

18. This was a tough one. 18 is 17 in base 9. They are the prime number 17 in different bases.10001 is binary for 17=1x16+0x8+0x4+0x2+1x1. 122 is 17 in base 3. 17=1x9+2x3+2x1 101 is 17 in base 4. 17=1x16+0x4+1x1.


Google is great

I was hoping someone was clever enough to figure it out for themselves...not pull it from the internet. It was an impressive quiz question

[Venture]

I was hoping someone was clever enough to figure it out for themselves...not pull it from the internet. It was an impressive quiz question
Sadly rockchick we don't use our brains nowadays. Just google.:(