Bob wants to build a pyramid out of legos with 3 levels where the bottom level has 7 legos per side and each level has one less lego per side than the level below it. How many legos total will he need?
Thoughts? Step-by-step reasoning:
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First find the total number of legos on the bottom layer: 7 legos * 7 legos = 49 legos. Then find the number of legos per side on the next layer: 7 legos - 1 lego = 6 legos. Then find the total number of legos on the second level: 6 legos * 6 legos = 36 legos. Then find the number of legos per side on the top level: 6 legos - 1 lego = 5 legos. Then find the total number of legos on the top level: 5 legos * 5 legos = 25 legos. Then add the number of legos on each level to find the total number of legos: 49 legos + 36 legos + 25 legos = 110 legos.
Thus, the answer is 110.
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