Finding Fractions on a RulerDate: 08/16/99 at 01:17:09 From: Brian Strope Subject: Defining Fractions of an Inch Dear Dr. Math, My question is simple. I want to know how to read all the measurements within 1 inch. We know that every line on a ruler or tape measure (whichever) has a fractional meaning. I want to learn how these fractions are arranged. I hope you understand what I mean by all fractions in an inch. Example: where is 7/8 of an inch compared to 5/16 of an inch on a tape measure? I know where the basic measurements are, such as 1/4, 1/2, and 3/4 of an inch. It's just the other measurements that I don't get. Thank you. F. Brian Strope Date: 08/16/99 at 11:17:58 From: Doctor Peterson Subject: Re: Defining Fractions of an Inch Hi, Brian. There's a lot of information hidden in a ruler, and it can take some practice to find it all. We have a very complete explanation of reading a ruler here in our archives: Reading a Ruler http://mathforum.org/library/drmath/view/58333.html I'll give you a simpler, quick answer that may meet your needs. Here's a ruler showing 16ths, with the meaning of each mark indicated: 0 1 | 1/2 | | | | | 1/4 | 3/4 | | | | | | | 1/8 | 3/8 | 5/8 | 7/8 | | | | | | | | | | | 1/16 | 3/16 | 5/16 | 7/16 | 9/16 | 11/16 | 13/16 | 15/16 | | | | | | | | | | | | | | | | | | +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ Some rulers only go to eighths, and it might be easier to start with that: 0 1 | 1/2 | | | | | 1/4 | 3/4 | | | | | | | 1/8 | 3/8 | 5/8 | 7/8 | | | | | | | | | | +-------+-------+-------+-------+-------+-------+-------+-------+ 0 1/8 2/8 3/8 4/8 5/8 6/8 7/8 1 As the marks go down in size, the denominator of the fraction doubles. The biggest mark between two inches is the half; between that and either inch mark the next largest mark is the quarter inch; and so on. To find eighths, just go down the scale finding 1/2, then 1/4, then 1/8. All the marks that are that size or bigger are eighths: 1/8, 2/8 (which is the same as 1/4), 3/8, 4/8 (which is the same as 1/2), 5/8, and so on. If you want, you can just count all the marks that are the same size, counting by odd numbers: 1/8, 3/8, 5/8, 7/8. Try doing the same thing on the 16ths ruler above; the only hard part will be to ignore the smaller 16ths marks while you're looking for 8ths. To find 5/8, for example, find which size marks are 8ths, then count 1, 3, 5/8 until you find it. Now you should be able to work out 32nds yourself: 0 1 | 1/2 | /2 | | | | 1/4 | 3/4 | /4 | | | | | | 1/8 | 3/8 | 5/8 | 7/8 | /8 | | | | | | | | | | 1/16 | 3/16 | 5/16 | 7/16 | 9/16 | 11/16 | 13/16 | 15/16 | /16 | | | | | | | | | | | | | | | | | | 1 | 3 | 5 | 7 | 9 | 11| 13| 15| 17| 19| 21| 23| 25| 27| 29| 31| /32 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ If you need any more help, feel free to write back. - Doctor Peterson, The Math Forum http://mathforum.org/dr.math/ |
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