21
The 20th triangular number is 20*21/2 = 210
32 is not a triangular number. The first few triangular numbers are 1, 3, 6, 10, 15, 21, 28, 36, 45, ...
Because it is ! The first 10 triangular numbers are... 1,3,6,10,15,21,28,36,45 & 55
No, 23 is not a triangular number. Here are a few examples of triangular numbers: 21, 28, 55, 45, 78 and 91.
21
The 20th triangular number is 20*21/2 = 210
21
32 is not a triangular number. The first few triangular numbers are 1, 3, 6, 10, 15, 21, 28, 36, 45, ...
Because it is ! The first 10 triangular numbers are... 1,3,6,10,15,21,28,36,45 & 55
28"21" but to be extra smart the answer is "The seventh triangular number is twenty one."
No, 23 is not a triangular number. Here are a few examples of triangular numbers: 21, 28, 55, 45, 78 and 91.
No. The first few triangular numbers are 1, 3, 6, 10, 15, 21, 28, ...
36 is the only square number that is also a triangular number between 20 and 40.
47 is not a triangular number. Triangular numbers less than 100 are 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, and 91.
6, 10, 15, 21, 55, 91...
Thre are infinitely many solutions. The smalest set with two different triangular number adding to another is 6 + 15 = 21