Brain Teasers
61, 691, 163
What number comes next in the sequence:
61, 691, 163, 487, 4201, ?
61, 691, 163, 487, 4201, ?
Hint
Reverse the digits of the numbers.Answer
9631. The sequence consists of the prime numbers which, when their digits are reversed, are perfect squares.Hide Hint Show Hint Hide Answer Show Answer
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Comments
good teaser!!
That would have taken some poring over to come up with it. I got the 'reverse squares' part only after reading the hint.
I got the hint, but it was still difficult.
my head hurts......
i have an alternate solution ...
the numbers reversed are squares of, in order, 4, 14, 19, 28, 32
which is 4+10+5+9+4 so the next should be +8 which = 40
40 squared is 1600 so reversed the answer is
0061
the numbers reversed are squares of, in order, 4, 14, 19, 28, 32
which is 4+10+5+9+4 so the next should be +8 which = 40
40 squared is 1600 so reversed the answer is
0061
yeah mdbiker, that's the way I did it. Recognizing the next prime # is much more difficult.
Nov 15, 2007
I have a different solution - the numbers reversed are squares, and the pattern of numbers is 3,9,4,8,3 ...
1 to 4*4 = 3, 16 to 14*14 = 9, then 4 to 19*19, then 8 to 28*28, then 3 to 32*32, ... next would be 9 to 42*42
1 to 4*4 = 3, 16 to 14*14 = 9, then 4 to 19*19, then 8 to 28*28, then 3 to 32*32, ... next would be 9 to 42*42
ugh. my head is leaking. that hurt. I don't like math any more........
This is not an original puzzle.
I agree with the 0061 answer, it also should be a valid answer as it follows a definite and predictable pattern.
4 14 19 28 32 40
15 14 13 12
4 14 19 28 32 40
15 14 13 12
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