Brain Teasers
3, 9, 33
Find the next three numbers in this sequence:
3, 9, 33, 129, 513, ?, ?, ?
3, 9, 33, 129, 513, ?, ?, ?
Hint
binAnswer
2049, 8193, 32769The numbers are the decimal form of the binary numbers when you take 11 (3), then add two 0's to the middle to get 1001 (9), and then add two more 0's to the middle to get 100001 (33) and so on:
11 = 3
1001 = 9
100001 = 33
10000001 = 129
1000000001 = 513
100000000001 = 2049
10000000000001 = 8193
1000000000000001 = 32769
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Comments
Veeeeery interesting! I didn't get it, but thought it excellent.
Good job. I actually got this 1 keep em' coming
I understood your answer, but I do believe you are getting a wee bit deeper than many every day *sharp and witty* people. Good luck with getting this one through, though.
Jan 15, 2007
i found the answer a different way... i multiplied the number by 4 and subtracted 3 and thats how i got the following answer.
gkitchen, your method is the same as the given answer, only put more simply. Multiplying by 4 in binary is like multiplying by 100 in decimal - you just add two zeroes to the end. You then have a binary number that ends with 100, from which you subtract 3, or 011. Binary 100 - 011 = 001. Therefore you get the pattern described in the answer!
If you work with configuring IP networks and subnetmasks etc a lot (and thus with powers of 2), this one is easy.
Still very nice!
Still very nice!
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