Final answer:
Triangular numbers are numbers that can form an equilateral triangle. To determine if 351 is a triangular number, we can use the formula n(n+1)/2 = 351, where n is the number of terms in the sequence. The number of terms is approximately 23.
Step-by-step explanation:
Triangular numbers are numbers that can form an equilateral triangle. They are expressed as the sum of consecutive positive integers starting from 1. To determine if 351 is a triangular number, we can use the formula n(n+1)/2 = 351, where n is the number of terms in the sequence. We can solve this equation by trial and error or by using algebra. In this case, the number of terms is approximately 23. Therefore, the answer is 23 (b).