Brain Teasers
1, 3, 7...
Complete the following series.
1, 3, 7, 13, 21, 31, ?, ?
1, 3, 7, 13, 21, 31, ?, ?
Answer
The next numbers are 43 and 57.(6*6)+6+1=43
(7*7)+7+1=57
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Comments
Way too easy, but You're thinking outside the box, I like that.
This is a very easy teaser, yet it was cool to think about it.
Using odd numbers.....1, 3 , (skip 5) , 7, (skip 9,11) 13, (skip 15,17,19) 21 etc.
I liked this math teaser. It was an easy one for me. The way I solved it was by counting by 2s and adding that to the next number in the sequence. (1, 3, 7, 13, 21, 31) So you just say 1+2 =3 and 3+4=7 and 7+6=13 and so on.
I thought the answer would be 43 based on :
If you look at the pattern of the numbers, you'll see that :
between the 1 and 3 = 0 odd num.
between the 3 and 7 = 1 odd (5)
between the 7 and 13 = 2 odd (9, 11)
between the 13 and 21 = 3 odd (15, 17, 19)
between the 21 and 31 = 4 odd (23, 25, 27, 29)
I was going with what Kay Ladi said, so I assumed it was way too easy as well. But there are infinitely many ways to name a mathematical series such as this one, so we're all right, I suppose.
theres too many possible answers to this one. Otherwise, good one, though a little easy.
I don't think I quite understand your explaination....
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