Which of the following circles is a circle of triangular numbers?
Triangular numbers are derived from the addition of consecutive natural numbers.
Natural Numbers: 1 2 3 4 5 6 7
1 1+2=3 1+2+3=6 1+2+3+4=10
So the series of numbers (1, 3, 6, 10, 15, etc.) obtained by continued summation of the natural numbers 1, 2, 3, 4, 5, etc is termed as triangular numbers.