The numbers 1, 3, 6, 10, 15, ... are known as triangular numbers. Each triangular number can be expressed as (n(n+1))/2 where n is a natural number. The largest triangular number less than 500 is: A) 16
B) 9
C) 8
D) 5
E) 3
Please include an explanation if you answer, thanks

Fill in the blank 1. a rhombus is a rectangle a) always b) sometimes c) never 2. a square is a quadrilateral a) always b) sometimes c) never 3. a trapezoid is a kite a) always b) sometimes c) never 4. a quadrilateral is a kite a) always b) sometimes c) never 5. a square is a rhombus a) always b) sometimes c) never 6. a parallelogram is a rectangle a) always b) sometimes c) never