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Topic: Rounding for science
Replies: 2   Last Post: Feb 25, 1997 3:35 PM

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Kate Jones

Posts: 2
Registered: 12/6/04
Rounding for science
Posted: Feb 22, 1997 8:04 PM
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Hi everyone,
I've been lurking in the background for some time now and thought I should
let you know I was here. The topic of rounding is an opportune topic to
introduce myself.

My name is Kate Jones and I am a PhD student in physics at the University of
New England in Australia. I also teach maths at the local TAFE (Technical
and Further Education) College.

Scientists use 'formal' rounding all the time when they consider the
accuracy of a measurement or the uncertanties associated with an experiment.

Example: radius of a circle = 2 cm therefore circumference =
12.56637061436 cm (from calculator). That number of decimal places is
nonsensical, so what do I round to? The answer depends on the equipment that
you used to measure the radius. Use of a metre ruler with, at best, a
minimum reading of 0.1 cm means you should round to 1 d.p. However, if you
had used a micrometer with a minimum reading of 0.001 you can round to 3
d.p., always using 'formal' rounding rules. Rounding is also important when
dealing with irrational numbers and the level of accuruacy you want in your

With maths and science being closely related I am sure this is why rounding
and sig. figures are dealt with at secondary school. If you have adult
learners with thoughts of gaining certificates in general education and then
moving on to university then formal rounding should be taught. I really
can't justify teaching this type of rounding to adults who want to survive
in the 'real' world.

Some other thoughts on the topic - most examples in the discussion so far
have been with rounding up in real life (e.g. money problems) how about the
case when you have a packet of 19 sweets that must be shared EQUALLY among 4
children. 19/4 = 4.75 but we would round down and give each child 4 sweets
and mum and dad would probably share the remainder. Also, in Australia, our
lowest monetary denomination is the five cent piece,5c. At the cash register
91c or 92c would be round down to 90c; 93c and 94c are round up to 95c; 96c
and 97c are round down to 95c and 98c and 99c are round up to $1.

Kate Jones

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