"Balls are arranged in rows to form an equilateral triangle. The first row consists of one ball, the
Channel: Doubtnut
Date: 05/04/2020

"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 669 more balls
 are added, then all the balls can be arranged in the shape of a square and
 each of the sides then contains 8 balls less than each side of the triangle
 had. The initial number of balls is
(a)
 1500 (b) 1540 
 (c) 1600 (d) 1690"