Latest MBA Aptitude Question SOLUTION: there are 8436 steel balls each radius 1cm stacked on top of each other, 1 on the top layer, 3 on next layer, 6th in third, 10th in 4th and so on. How many horizontal layers are pr

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(#M40039671) MBA Numerical Ability question Progression based problem Keep an EYE

there are 8436 steel balls each radius 1cm stacked on top of each other, 1 on the top layer, 3 on next layer, 6th in third, 10th in 4th and so on. How many horizontal layers are present?

Asked In MBA adit mishra (9 years ago)

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shabih abbas  (9 years ago)

There is 1 ball on the top layer, (1+2) ball on the next layer, (1+2+3) ball in the next layer. So in Tn=(1+2+3...n)
Tn=n(n+1)/2
so Sum= summation of (n(n+1)/2)
=summation of (n^2+n)/2
=n(n+1)(2n+1)/12 + n(n+1)/4
on solving, we get
n(n+1)(n+2)/6= 8036
n(n+1)(n+2)= 50616
n(n+1)(n+2)=36*37*38
so, n=36

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