antel0pe Posted February 2, 2014 Report Share Posted February 2, 2014 A certain ruler, which is supposed to be 12 in long, is warped and is actually just 11 1/2 in. If you measure off 4 ft of string with this ruler, what is the percentage error in your measurement? Quote Link to comment Share on other sites More sharing options...
0 bonanova Posted February 3, 2014 Report Share Posted February 3, 2014 Sounds like a homework problem. Percentages are nice - they are invariant to scale. So here's a clue: what is the percentage change in the length of the ruler? Quote Link to comment Share on other sites More sharing options...
0 skca Posted February 4, 2014 Report Share Posted February 4, 2014 4.166% change in the length of the ruler Quote Link to comment Share on other sites More sharing options...
0 harey Posted February 4, 2014 Report Share Posted February 4, 2014 (edited) There might be a trap. Back to the secondary school for the definition of the measurement error. I have rulers which are divided in cm and subdivided in 1/10 of cm. If I tell you I mesured 2.4 cm, you assume the the value is between 2.35 and 2.45. Error in percentace=0.1/2.4*100 If I tell you I mesured 7.4 cm, you assume the the value is between 7.35 and 7.45. Error in percentace=0.1/7.4*100 I happen to have a curiosity of a ruler in inches. It's subdivisions are 6 (for 6 lines per inch or 12 cpi), 8 (for 8 lines per inch or 8 cpi) and 10 (for 10 cpi). (Supposing this ruler shrinked by 1/24, I get a headache.) If antelOpe has such a ruler, the error is 1/subdivison/4*100. Edited February 4, 2014 by harey Quote Link to comment Share on other sites More sharing options...
0 antel0pe Posted February 4, 2014 Author Report Share Posted February 4, 2014 4.166% change in the length of the ruler Yep, that's the answer. There might be a trap. Back to the secondary school for the definition of the measurement error. I have rulers which are divided in cm and subdivided in 1/10 of cm. If I tell you I mesured 2.4 cm, you assume the the value is between 2.35 and 2.45. Error in percentace=0.1/2.4*100 If I tell you I mesured 7.4 cm, you assume the the value is between 7.35 and 7.45. Error in percentace=0.1/7.4*100 I happen to have a curiosity of a ruler in inches. It's subdivisions are 6 (for 6 lines per inch or 12 cpi), 8 (for 8 lines per inch or 8 cpi) and 10 (for 10 cpi). (Supposing this ruler shrinked by 1/24, I get a headache.) If antelOpe has such a ruler, the error is 1/subdivison/4*100. Also thanks for the creative and enthusiastic approach, harey. Quote Link to comment Share on other sites More sharing options...
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antel0pe
A certain ruler, which is supposed to be 12 in long, is warped and is actually just 11 1/2 in. If you measure off 4 ft of string with this ruler, what is the percentage error in your measurement?
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