Question

There are 8436 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. Determine the number of horizontal layers in the pile ?

• A. 32
• B. 36
• C. 96
• D. 34
• E. 24

Hint:

The sequence of sums of triangular numbers is called Tetrahedral Numbers. Knowing the $n(n+1)(n+2)/6$ formula saves you from manually integrating series progressions during timed exams.

Answer 1

The Correct Option is B