I remember a Course II question from years ago...I think it involved the area of a trapezoid.  If the students rounded during the intermediate steps, their answer was off by NINE units!  I always used to use this one as an example of the 'dangers' of rounding before the end..it made an impression.
It seems to me that it is extremely important that students are taught not to round before the end of a problem (whether they complain about it or not). 
In general, by the way, they think we're nuts!  Let me see...it's 9:00 at night, and I'm writing an email extolling the virtues of not rounding before the end...they may have something there:)
Liz Waite



-----Original Message-----
From: Daniel Knaisch <dknaisch@elmiracityschools.com>
To: nyshsmath <nyshsmath@mathforum.org>
Sent: Wed, May 4, 2011 11:08 am
Subject: RE: On Regents Exam

Never had the pleasure of teaching Course 3, Started teaching during the reign of Math B. Although I know the importance of using all decimals displayed, when communicating that to students you can actually see my voice going through one ear and out the other (its an amazing sight). As I am lecturing on the importance, the reality still is these kids are thinking "if he thinks I am writing down all these numbers, this guy is nuts." Storing the number for a variable cures this problem, but again getting some of these kids to know the calculator keys is a tough job in itself. There is probably no way to get all kids to do what you ask them to anyway, and if you are getting every student to use the full display, then you should be deemed as teacher of the year. Regardless, Until I see a quesion where 4-decimals is not enough (in the Alg2/Trig), I have thrown in the towel on trying to get these kids to use the full display. I do mention it, and those of them that actually pick up on the importance can/will do it.
 
would love to see the question where 4-decimals was not enough.
 
Daniel Knaisch
Math Teacher
Elmira Free Academy
933 Hoffman St.
Elmira, NY 14905
(607)735-3100 ext 4233
 
From: owner-nyshsmath@mathforum.org [owner-nyshsmath@mathforum.org] On Behalf Of T Dempsey [dempseyt53@gmail.com]
Sent: Wednesday, May 04, 2011 10:18 AM
To: nyshsmath@mathforum.org
Subject: Re: On Regents Exam

Many years ago (Course 3!) I had students round to the 4th place and told them that should cover it. I was wrong. Many lost 1 point. Since then, we hold the full display of the calculator.  

On Wed, May 4, 2011 at 8:32 AM, Daniel Knaisch <dknaisch@elmiracityschools.com> wrote:
From my experience, students are lazy and when they see the calculator spit out a decimal that is 8 or 9 places long, you start hearing the moaning and complaining that they have to use them all (even from the best students). This is a battle that you just won't win, so I have always told them to round to 4 decimal places no matter what. Going back to the "old days" when we used trig tables (some of you young bucks won't remember), but all of the decimals were rounded to 4 places. I have never come across a problem where rounding was skewed becasue of using only 4-decimals

Daniel Knaisch
Math Teacher
Elmira Free Academy
933 Hoffman St.
Elmira, NY 14905
(607)735-3100 ext 4233
________________________________________
From: owner-nyshsmath@mathforum.org [owner-nyshsmath@mathforum.org] On Behalf Of mathpig [mirie@northvillecsd.k12.ny.us]
Sent: Tuesday, May 03, 2011 6:45 PM
To: nyshsmath@mathforum.org
Subject: On Regents Exam

There is a question using both the law of Sines and Cosines, and first you solve for a side and use it to find an angle. Say the side is an irrational number (ex. 10.254873209). Can a student round it to say the nearest hundredth and use it to solve an angle OR should a student use the 10.254873209 to solve the angle?

I have always taught students to use the number and not to round it until the end (the answer) but just wondered if that is allowed.
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