### Brain Teasers

# 1, 3, 6

Your numbers are as follows:

1, 3, 6, 10, 15, 21, 28

What will be the 12th number?

1, 3, 6, 10, 15, 21, 28

What will be the 12th number?

### Hint

Look at the order of the number. I.E. 1 was 1. 2 was 3.### Answer

78. Take the order of what I am asking you. That is 12. Then take that number (12) and multiply it by the number following it. (13) Then divide it by 2. You have your answer. This is also called the triangle puzzle.Hide Hint Show Hint Hide Answer Show Answer

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## Comments

i did it another way for example i went 1+2=3 then just add one to the 2 so the next one would be 3+3=6 and then 6+4 and so on (r u with me) good teaser though i enjoyed it

i guess you could do it that way, thats pretty clever. Thanks, I'm glad you liked it!

brlliant teaser- Nutty

There is another way. If you see the series it goes 1, 1+2=3,3+3=6,6+4=10, so on. This can be continued till you get 66+12. In other words you add the position to your previous number to get the next number.

I used the formula {(N^2)+N}/2

THATS A JUNIOR SCHOOL, SIMPLE, EASY MATHS QUESTION

I saw it as the sequence A x B, where A = 1,1,2,2,3,3,4,4,5,5,... and B = 1,3,3,5,5,7,7,9,9,...

I'm surprised at the surprise. The triangular numbers are generally well known by primary school children in our country.

+2, +3, +4, +5, +6, +7, ...so +8 = 36.

ah, 12th number - missed that!

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