Math CentralQuandaries & Queries


Question from Sam:

I had a carpenter being a smarty pants with me. Question: I have a 20ft piece of pipe. I need three equal lengths cut. What is the measurement of each cut? He told me the answer right away because he knows the measuring tape like the back of his hand. The answer is 6'8". Is there an equation I can use to get the answer quicker than him looking at his tape measure?

Hi Sam,

Your carpenter has done this sort of calculation so often it is second nature to him. This is how would do it.

3 × 6 = 18 so each piece is 6 feet long plus a little bit. 20 - 18 = 2 so you have 2 feet to split 3 ways. Two feet is 24 inches and 24/3 = 8 so each piece get an additional 8 inches. Hence each piece is 2 feet 8 inches long.


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