engineering recuitment GATE ME 2023-24 Test Series Quantitative Aptitude Permutation and Combination
There are 220 steel balls, each with a radius of 1 centimeter, stacked in a pile, with 1 ball on top, 3 balls in the second layer, 6 in the third layer, 10 in the fourth, and so on. The number of horizontal layers in the pile is:
1
12
2
15
3
10
4
20