Question 330237
Can someone please walk me through this? 
Plastic pipe is stacked so that the bottom row has 25 pipes, the next row has 24 pipes, the next row has 23 pipes, and so on until there is 1 pipe at the top of the stack. If a worker removes the top 17 rows of pipe, how many pieces of pipe will be left in the stack?
___ pieces of pipe 
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The total number of pipes is 1+2+3+...+23+24+25
= (25/2)(1+25) = 325
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The top 17 rows have 1+2+3+4...+15+16+17
= (17/2)(1+17) = 153
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You can figure out how many are left after removing 153 of the pipes.
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Cheers,
Stan H.
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