Math Problems, Proportions Problems

Problem of the Day: 2/20/13

Kelly walks her dog around her block in 20 minutes. She knows that 3 of these blocks is half a mile. In how many minutes can she walk her dog around her friend’s block, two of which constitute a mile?

Solution to yesterday’s problem:

Let’s represent the problem with two linear equations. The first one, the supply equation/curve, has a slope of 100,000 because that’s how many is added for each $1 increase. So we can write that equation as


The demand equation has a y-intercept of 1,000,000 because that’s how many people would get the product at price zero. The slope is -300,000 because 300,000 less people would get it for each $1 increase. So the demand equation is


The point where supply and demand are equal is the intersection of these two lines. We can find this point by setting the two equations equal to each other:


Solving this equation,


(Dividing by 100,000 to make the numbers a bit easier)



So Company X should theoretically price Product X at exactly $2.50.


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