HP Forum Archive 05

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An HP 17BII equation challange for all who love problem solving using a calculator Message #1 Posted by Mike Burns on 20 Feb 2001, 10:04 a.m. The original book equation for speed walking aerobic fitness points. PT=(Dx60/T)-1)xD-1 e.g. (2x60/30)-1)x2-1=5 points Where PT=points, D=distance(2miles), & T=time(30 minutes). . This is the 1st calculator equation : SPM=((MIN+SEC/60)/(BLK x .435)-13)x60. Where SPM=seconds per mile (based on a 13 minute mile). BLK= .435 of a mile the distance around my neighborhood block. The variables are: SPM. MIN. SEC. BLK . . Lets say I went 3 times around the block in 17 minutes and 25.31 seconds and my total walking time was 22 minutes. Therefore; MIN=17 SEC=25.31 BLK=3 SPM=??? ANSWER is 21 seconds per mile because its based on 13 minute mile I know my speed per mile is 13:21 . Now my 2nd equation in my HP 17BII has to do with my total walking time. I used an equation for distance to combine two equations into one: D=(T/(SPM/60+13). Time divided by speed = distance therefore 22/13:21 (21/60+13) is the same as (SPM/60+13) the answer is 1.65 miles is the distance. and the points PT=4.76 This is the answer you should get in the 2nd equation below Therefore; PT=(T/(SPM/60+13)x60)/T-1x(T/(SPM/60+13)-1) is the same as PT=(Dx60/T)-1)xD-1 The variables are PT.. T.. SPM. When working out equation in a step by step procedure it only works out properly up to this point PT=(T/(SPM/60+13)x60)/T-1 If you put in the equation up to this point using T=22 (my total walking time was 22 minutes) and SPM=21 then PT=?? answer 3.49 is the right answer up to this point. when I put the rest of the equation i.e. x(T/SPM/60+13)-1) in the answer is 3.85 for PT but the correct answer for PT is 4.76 as you can see (T/SPM/60+13) is repeated twice in the equation because it represents D for distance based on the original book equation The HP 17BII is not interpreting this aspect properly. How do I represent this equation so that this aspect is taken into account? Thanks! .

Please don't ask the same question in three threads Message #2 Posted by Dave Hicks on 20 Feb 2001, 12:05 p.m., in response to message #1 by Mike Burns Mike, as I said the first time you posted this, your parens are in the wrong place. The calculator is doing the right thing. Your expression: (T/(SPM/60+13)x60)/T-1x(T/(SPM/60+13)-1) = 3.85 Correct expression: ((T/(SPM/60+13)x60)/T-1)xT/(SPM/60+13)-1 = 4.76

Re: Please don't ask the same question in three threads Message #3 Posted by Mike Burns on 21 Feb 2001, 4:12 p.m., in response to message #2 by Dave Hicks Thanks Dave I greatly appreciate your help! How did you know exactly what to do with parens. Is it your math knowledge or did you get from a manual? Is there a manual such as vol 1 of the CD's available for purchase on this web site that would have helped me?

Re: Please don't ask the same question in three threads Message #4 Posted by Dave Hicks on 22 Feb 2001, 12:13 a.m., in response to message #3 by Mike Burns It's math/algebra rules. You started with: PT=((Dx60/T)-1)xD-1 but while doing your substitution, you modified the main formula to: PT=(Dx60/T)-1x(D-1) That totally changes the result. Now you're subtracting D-1 rather than multiplying by D and subtracting 1. I don't know of any calculator books that cover this. It's an algebra textbook subject. From the calculator's perspective it's garbage in => garbage out.

Re: Please don't ask the same question in three threads Message #5 Posted by Mike Burns on 22 Feb 2001, 11:58 a.m., in response to message #4 by Dave Hicks David I respect your knowledge and truly appreciate your help!!. I checked my equation. This is the right one PT=(Dx60/T-1)xD-1 In my original question this PT=(Dx60/T)-1)xD-1 was incorrectly written and is an invalid equation according to my HP 17BII. I see your logic clearly with regard to PT=(Dx60/T-1)xD-1 What I would like to know is why the two (( at the beginning of this equation ( (T/(SPM/60+13)x60)/T-1)xT/(SPM/60+13)-1. How did you know it need two(( I know with only one ( the equation is invalid but if I put two parens on this equation ((Dx60/T-1)xD-1 my HP 17BII consider this equation invalid. Therefore; is there a rule of thumb? Thanks P.S. Did Jim Lawson publish a pamphlet he used as a sales tool when Handicalc was in business that described the contents of each of these 5 manuals: There are several application manuals for the 17B/27S/19B Pioneer calculators: (1) Real Estate, Banking & Leasing; (2) Business Finance & Accounting; (3) Marketing & Sales; (4) Personal Investment, and (5) Technical Applications. If this is correct how do I get in contact with him directly

Re: Please don't ask the same question in three threads Message #6 Posted by Dave Hicks on 22 Feb 2001, 12:38 p.m., in response to message #5 by Mike Burns You originally posted: PT=(Dx60/T)-1)xD-1 That is not a valid equation (to an HP-17Bii or anyone else) because the parentheses are not balanced. This sentence looks strange) doesn't it? The closing parenthesis after strange doesn't match an opening parenthesis. I just added '(' to make it valid. Like: PT=((Dx60/T)-1)xD-1. I could have also deleted one like: PT=(Dx60/T-1)xD-1. Both of these are valid equations and are equivalent. Since I didn't have access to the original equation, I guessed its form and then verified it by plugging in the numbers you gave as examples. Re Mr. Lawson - I don't know. Generally, people don't post "I don't know" to keep the forum from filling up with that answer.

Re: Please don't ask the same question in three threads Message #7 Posted by Matt Kernal on 22 Feb 2001, 6:19 p.m., in response to message #5 by Mike Burns Mike Burns> Therefore; is there a rule of thumb? I hope I'm correctly understanding the question you're asking, but beyond having balanced parentheses, yes there is a rule of thumb. Call it what you like, order-of-operations, priority, or precedence, the memory aid I remember is.. PEMDAS (Please Excuse My Dear Aunt Sally) where: P = Parentheses E = Exponents M = Multiplication (same priority as division) D = Division (same priority as multiplicaton) A = Addition (same priority as subtration) S = Subtraction (same priority as addition) Which means "before anything else, do what's inside the parentheses. Next, if there are any exponenents, apply that power to the result of what was inside the parentheses. Next, if there is a division OR multiplication, apply that operation next. And finally, if there is any addition OR subtraction to do, apply it last". On a related note to Dave... I noticed your description of the HP-17B calculator mentions it has "full algebraic logic including precedence". By accident, I found mine doesn't recognize precedence. Recently, HP's Jean-Yves Avenard pointed that only the algebraic scientifics recognize precedence (like the 6S, 20S, 21S, 22S, 27S, 30S, 38G, 39G), but the algebraic business calculators do not (17B, 17BII for sure; I haven't tested the 10B, 14B, 19BII). I asked him why the inconsistency? After all, they aren't called "calculators" for nothing. He said it was an industry standard; Ti and Casio do the same. I haven't noticed if this is actually true. To be safe, know your order-of-operations, and never stray away from RPN :-) Matt

Re: Please don't ask the same question in three threads Message #8 Posted by Steve (Australia) on 22 Feb 2001, 8:48 p.m., in response to message #7 by Matt Kernal Or BIMDAS Brackets, Indicies, ....

Re: Please don't ask the same question in three threads Message #9 Posted by Dave Hicks on 23 Feb 2001, 2:55 p.m., in response to message #7 by Matt Kernal Thanks Matt! I'll correct that.

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