Logs are stacked in a pile. The top row has 15 logs and the bottom row has 24 logs. How many logs are there in the stack?

Question

jim_thompson5910 · Answer

You can do it the long way

15+16+17+18+19+20+21+22+23+24

OR

You can use the formula

S = (n*(first term + last term))/2

Where n is the number of terms

anonymous · Answer

Do we just assume that each succeeding stack will have 1 log less that the previous one (starting from bottom n going upward)  ????

jim_thompson5910 · Answer

yes, I'm assuming that the log stack is a pyramid

jim_thompson5910 · Answer

|dw:1341347491683:dw|

jim_thompson5910 · Answer

lol something like that

anonymous · Answer

But this assumption is not supported by any fact from the question.....

jim_thompson5910 · Answer

true, but you can imagine stacking logs like that, so I don't see why not

jim_thompson5910 · Answer

hopefully the picture I drew makes sense

anonymous · Answer

Yeah, that way it works out but I guess there must be another way without this assumption...
Anyone with any other solution???

jim_thompson5910 · Answer

hmm how else would you stack it? You can't exactly stack one log on top of the other (without support from another log). Besides, the number of logs decreases as you go up, so that's mostly why I made that assumption.

anonymous · Answer

I know that intuitively this is right but.........???

jim_thompson5910 · Answer

good point, they might use other means to stack it...but I'm still sticking to my original answer