On 9/20/2010 4:48 PM, Paul T Williams wrote: > Hi all, > > Are you as smart as an 8th grader? > > I pay my son 8 cents for every problem he gets correctly solved and > fine him 5 cents for each incorrect solution. At the end of 26 > problems, neither owes anything to the other. How many problems did > the boy solve correctly? > > What the algebraic solution here? > Paul Okay, you want algebra .... a dinosaur can still provide it, still preserved from back in Grade 7. (Probably preserved by lack of use?) x = problems done right y = problems done wrong x + y = 26 8x - 5y = 0 5y = 8x (You add 5y to both sides) y = (8/5)x (you divide both sides by 5) x + (8/5)x = 26 (you substitute to express y in terms of x) Easier to write 8.5 as 1.6. Hence x + 1.6x = 26 2.6x = 26. X is 10. --------------- Test the work: 10 problems right times 8 cents = 80 cents 16 problems wrong times 5 cents = 80 cents -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/caut.php/attachments/20100920/25ec1a01/attachment.htm>
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