Question 326182
the 12th layer (11 layers above the 1st layer) has 20-11 or 9 poles in it


the 11th layer has 10 poles...and so on


the 1st layer plus the 12th layer is 29 poles ___ the 2nd layer plus the 11th layer is 29 poles ___ and so on


the total is ___ (1/2) * 12 * 29