Too fast Gengar
Gengar plans to build a conical shape by placing balls one on top of the other in rows.
The first row has 1 ball, the second has 6, the third has 20, the fourth has 56 balls, fifth has 144, sixth has 352 and so on.
He arranges a total of 32 rows. If keeping each ball in its designated position took him seconds, then find the number of minutes it takes for him to build the entire cone.
Details and Assumptions
You may use a calculator.
Take integral part of seconds to find minutes and give integral part of minutes found as answer.
The answer is 8733.
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1 solution
It just is an arithmetic geometric progression with a=1, r=2, d=2 and n=32.
Solving it, we get total number of balls as 261993005059. Time in seconds as 523986.01 and in minutes as 8733.1.
So answer is 8 7 3 3