Some identical balls are arranged in rows to form
an equilateral triangle. The first row consists of one
ball, the second row consists of two balls and so
on. If 99 more identical balls are addded to the total
number of balls used in forming the equilaterial
triangle, then all these balls can be arranged in a
square whose each side contains exactly 2 balls
less than the number of balls each side of the
triangle contains. Then the number of balls used to
form the equilateral triangle is :-