Question 23
The triangular number sequence is 1,3,6,10,15,21,28,36,45,… . These numbers count dots arranged in triangles, as shown. How many dots are in the 60th triangle?
In the original figure, “dot/dots” means “chấm”; the numbers below the triangles are their positions in the sequence.
In the original figure, “dot/dots” means “chấm”; the numbers below the triangles are their positions in the sequence.