Latest general Aptitude Question SOLUTION: One side of the bottom layer of a triangular pyramid has 12 balls. How many are there in the whole pyramid? Note that the pyramid is equilateral and solid.

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(#M40000197) GENERAL question Keep an EYE

One side of the bottom layer of a triangular pyramid has 12 balls. How many are there in the whole pyramid?
Note that the pyramid is equilateral and solid.

Asked In general Naveen (14 years ago)

Solved Tijo Jose Read Solution (2)

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Tijo Jose  (14 years ago)

Bottom layer contains (12+11+10+...+1) = 12*13/2 = 78 balls.
Immediate top layer contains (11+10+...+1) = 66 balls.
Similarly, the number of balls in the layers from top to bottom are 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78. Total = 1+3+6+10+15+21+28+36+45+55+66+78 = 364 balls

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Tijo Jose  (14 years ago)

364

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