SOLUTION: If a stack of n layers of power poles contains four poles in the top layer and each layer contains one more pole than the layer above, find how many layers there are if the stack c

Question 1034471: If a stack of n layers of power poles contains four poles in the top layer and each layer contains one more pole than the layer above, find how many layers there are if the stack contains 184 poles. Please help, Im not sure which formula(s) to use.
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
(1/2)n*(n+1) is the sum of all the numbers from 1 to n.
From 1 to 3 is a total of 6, so the answer would be the stack of 190 poles. We just ignore the first 3.
380=n(n+1)
n^2+n-380=0
(n+20)(n-19)=0
positive root only, n=19
16 layers, because we ignore the first 3.
4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19=184
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