The Number Rainbow - 12/04/2013
Posted: Fri Apr 12, 2013 7:18 amWhich number is not like the others in this number rainbow?
Why?
15
28
45
56
78
91
Why?
15
28
45
56
78
91
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The Number Rainbow - 12/04/2013
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Posted: Fri Apr 12, 2013 7:18 amRe: The Number Rainbow - 12/04/2013
Posted: Wed Apr 17, 2013 2:56 pm78
Re: The Number Rainbow - 12/04/2013
Posted: Wed Apr 17, 2013 7:32 pmCan you please explain how did you reach that answer?
Re: The Number Rainbow - 12/04/2013
Posted: Fri Apr 19, 2013 6:39 amSince I didn’t received an explanation of that answer I highlighted as incorrect.
The correct answer is 56 and it was successfully solved by Sergey Sokolov via facebook.
The pattern here is adding all the numbers up to N. This are called the triangular numbers and I have already published a sections with them.
1
1+2 = 3
1+2+3 = 6
1+2+3+4 = 10
1+2+3+4+5 = 15
1+2+3+4+5+6 = 21
1+2+3+4+5+6+7 = 28
1+2+3+4+5+6+7+8 = 36
1+2+3+4+5+6+7+8+9=45
1+2+3+4+5+6+7+8+9+10=55
1+2+3+4+5+6+7+8+9+10+11=66
1+2+3+4+5+6+7+8+9+10+11+12=78
1+2+3+4+5+6+7+8+9+10+11+12+13=91
Therefore 56 is the wrong number in this number set! It’s not triangular number
The correct answer is 56 and it was successfully solved by Sergey Sokolov via facebook.
The pattern here is adding all the numbers up to N. This are called the triangular numbers and I have already published a sections with them.
1
1+2 = 3
1+2+3 = 6
1+2+3+4 = 10
1+2+3+4+5 = 15
1+2+3+4+5+6 = 21
1+2+3+4+5+6+7 = 28
1+2+3+4+5+6+7+8 = 36
1+2+3+4+5+6+7+8+9=45
1+2+3+4+5+6+7+8+9+10=55
1+2+3+4+5+6+7+8+9+10+11=66
1+2+3+4+5+6+7+8+9+10+11+12=78
1+2+3+4+5+6+7+8+9+10+11+12+13=91
Therefore 56 is the wrong number in this number set! It’s not triangular number