# puzzle of the day

sona gold

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John Lee

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posted 13 years ago

I will try my best:

The top layer side length is 1 ball, layer sum is 1 ball;

The second layer side length is 2, layer sum is 3;

..................

So: sum = 1 + 2 + ... + side length = 1/2 * ( length + 1) * length;

................

So the twelveth layer has 78 ;

So the grand total is:

1 + 3 + 6 + 10 + 15 + 21 + 28 + 36 + 45 + 55 + 66 + 78 = 364 !

- 0

Originally posted by sona nagee:

one side of the bottom layer of a triangular pyramid has 12 balls. How many are there in the whole pyramid?

I will try my best:

The top layer side length is 1 ball, layer sum is 1 ball;

The second layer side length is 2, layer sum is 3;

..................

So: sum = 1 + 2 + ... + side length = 1/2 * ( length + 1) * length;

................

So the twelveth layer has 78 ;

So the grand total is:

1 + 3 + 6 + 10 + 15 + 21 + 28 + 36 + 45 + 55 + 66 + 78 = 364 !

sona gold

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Johnson Chong

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Johnson Chong

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Posts: 210

posted 13 years ago

- 0

Don Liu

Calculus of probabilities???!!!

What is that?

I've heard of calculus and probabilities but I just don't think I'll be able to find calculus of probabilities as a mathematical topic.

But I must say what a word.

Calculus of probabilities???!!!

What is that?

I've heard of calculus and probabilities but I just don't think I'll be able to find calculus of probabilities as a mathematical topic.

But I must say what a word.

-Surfing the JavaRanch in a sunny garden with a cold drink and laptop can't be beat. by Frank Carver(sheriff)

Jim Yingst

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Posts: 18671

posted 13 years ago

- 0

One of the definitions of calculus is "A system or method of calculation". So "calculus of probabilities" just means "calculation of probabilities". As it happens though, serious probability theory has

*lots*of integrals in it, so you definitely need a good grasp of [integral] calculus to understand it."I'm not back." - Bill Harding, *Twister*