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.
Answers were Sorted based on User's Feedback
Answer / keyur
I think there are 78 Balls..
At bottom Layer has 12 balls.Above that 11 balls are there.
In this Way 12,11,10,9,8,7,6,5,4,3,2,1.
So tptal balls are 78..
| Is This Answer Correct ? | 8 Yes | 4 No |
Answer / guest
There are total 364 balls.
As there are 12 balls along one side, it means that there
are 12 layers of balls. The top most layer has 1 ball. The
second layer has 3 (1+2) balls. The third layer has 6
(1+2+3) balls. The fourth layer has 10 (1+2+3+4) balls. The
fifth layer has 15 (1+2+3+4+5) balls. Similarly, there are
21, 28, 36, 45, 55, 66 and 78 balls in the remaining layers.
Hence, the total number of balls are
= 1 + 3 + 6 + 10 + 15 + 21 + 28 + 36 + 45 + 55 + 66 + 78
= 364 balls
| Is This Answer Correct ? | 11 Yes | 8 No |
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