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## Knotty Notation

Math brain teasers require computations to solve.

 Puzzle ID: #29087 Fun: (2.45) Difficulty: (2.49) Category: Math Submitted By: kiss Corrected By: shenqiang

A single drop of water contains 1.70 quintillion molecules. In the chemistry lab, I'm following a procedure that calls for me to add 30 drops of water to a solution. I must report how many hydrogen atoms I have added to the solution. I must write the answer in scientific notation.

What should I report?

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 thompson1 Mar 13, 2006 WOOHOO! First comment! I got it pretty easily, but I almost forgot about the amount of Hydrogen in water molecules. Good Teaser!! soccerstar_1515 Mar 13, 2006 cool cool Woden Mar 14, 2006 I liked it. My only disagreement would be the number of significant figures. I'm a chemistry major. The answer I have was 1.0*10^20. Only one decimal place. I thought that was the trick. Cool, though. paul726 Mar 16, 2006 I've always been taught to use two digits after the decimal when using scientific notation. cms271828 Mar 19, 2006 Too easy, usually figures are taken to 3 significant figures when you have to round. stil May 09, 2006 Number of significant figures in result are dependent on input. When multiplying or dividing numbers, find the number with the fewest significant figures, then round the result to that many significant figures. javaguru Feb 04, 2009 There as only two significant figures. Also, the size of the drop can vary, so presumably the number of molecules per drop given is based on the size drop produced by the pipet used to add the drops. If 1.02 x 10^20 was the desired answer then the number of molecules per drop should have been given as 1.70 quintillion. javaguru Feb 04, 2009 I see the teaser was corrected already. eighsse Sep 25, 2013 Fun and simple. I like it!