Triangle NumbersSeries teasers are where you try to complete the sequence of a series of letters, numbers or objects.
Triangle numbers are formed by adding successive integers, i.e.
1 = 1+0,
3 = 1+2,
6 = 1+2+3,
10 = 1+2+3+4,
So the first few triangle numbers would be:
Suppose somebody tells you a random integer. How can you quickly find out whether or not it is a triangle number?
HintThe method is linked to another common series.
AnswerMultiply the number by 8 then add 1. If the result is a perfect square, then the original number is a triangle number.
For example: 10*8+1 = 81. 81 = 9^2. So 10 is a triangle number.
11*8+1 = 89. 89 is not a perfect square, so 11 is not a triangle number.
See another brain teaser just like this one...
Or, just get a random brain teaser
If you become a registered user you can vote on this brain teaser, keep track of
which ones you have seen, and even make your own.
Back to Top