Mathematical Word Problems – Construction Tool
Do your kids have to practice solving mathematical word problems? Maybe they need to practice more during school breaks? I've written a function that can turn you in to a machine for torturing your kids with some.
Actually, this started off as a tool to find the date on which I was X times older than a colleague. It's super simple to do this with the help of the datetime datatype in MATLAB.
How does it work?
Given the birthdates for the elder and younger person, we want to return the date on which the elder is N times older than the younger one. Let's try it.
elderdate = datetime(1950, 1, 1); youngerdate = datetime(1992, 7, 17); doubledate = ntupleday(2, elderdate, youngerdate)
From there, it's just a matter of creating the relationships between various people, basically a set of linear constraints, and you are ready to embellish the stories as a new torture device for your kids. problems with for your kids to solve.
It was super easy to vectorize this, with respect to dates.
dd = datetime(1950, 1, 1:3:28)'; yd = datetime(1992, 7, 17:3:44)'; nd = ntupleday(2,dd,yd)
nd = 10×1 datetime array 31-Jan-2035 03-Feb-2035 06-Feb-2035 09-Feb-2035 12-Feb-2035 15-Feb-2035 18-Feb-2035 21-Feb-2035 24-Feb-2035 27-Feb-2035
Or for the multipliers
multiplier = 1.5:0.5:4.5; newdates = ntupleday(multiplier, elderdate, youngerdate); newdates'
ans = 7×1 datetime array 16-Aug-2077 31-Jan-2035 25-Nov-2020 24-Oct-2013 23-Jul-2009 21-Sep-2006 11-Sep-2004
What's the trend?
plot(newdates,multiplier, "-*") ylabel("Age Multiplier") xlabel("Date")
Clearly, we can't expect the younger person to actually catch up in age to the older one - just likely that the difference gets less significant over time.
And Then I Realized...
I then realized there was nothing so special with dates except the format. So this can also be used for entities with other units, if you need to work that in.
Improvements to Be Made
It would be great to add the full functionality for building the problems. I leave that as an exercise for you. E.g., what functions should I add if I want to be able to construct a problem given one date, say the elder, and have it spit out what the birthdate would if the child was 3 years and 2 months younger than half dad's birthdate.
Do you take advantage of datetime in MATLAB? Especially if you have something novel you are doing with it, please share your thoughts here.
The Function ntupleday
function ndate = ntupleday(n, bdelder, bdyounger) % The date on which the elder is n times as old as the younger % NTUPLEDAY returns the date when the OLDER person is N times the age of % the YOUNGER one. Using this, parents can torture their children by % making up a suite of word problems for the kids to solve. % % Example: % bdelder = datetime(1955,11,19); % bdyounger = datetime(1987,3,29); % doubleDate = ntupleday(2,bdelder, bdyounger) ndate = bdyounger + (bdyounger-bdelder)./(n-1); % Set the format of the output date to be the same as the first input date. % If the input is of type "datetime". Otherwise, don't worry about the % format. if isa(bdelder, "datetime") % ndate.Format = 'dd-MMM-uuuu'; ndate.Format = bdelder.Format; end end %ntupleday
doubledate = datetime 31-Jan-2035
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