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Expert: Robi Bhattacharjee - 6/13/2009


Question
Suppose that a market research company finds that at a price of p = $20, they would sell x = 42 tiles each month.  If they lower the price to p = $10, then more people would purchase the tile, and they can expect to sell x = 52 tiles in a month's time.  find the equation of the line for the demand equation.  Write your answer in the form p = mx divided by b.  (hint: write an equation using two points in the form (x, p).  ***I need to see how you arrive at the answer, I have worked on this all week and don't even know where to begin.

Answer
Hi Lori,

The first step with word problems is to get rid of the words. We do this by extracting all of the actual math.

So this reduces to

at x = 42, p = 20

at x = 52, p = 10

And we are to find an equation for p in terms of x. We do this by using point slope form.

So the slope = rise/run = (10 - 20) / (52 - 42) = -10/10 = -1.

So now we use are point slope form.

(slope)(x - 42) = p - 20

(-1)(x-42) = p - 20

-x + 42 = p - 20

p = -x + 62

I hope this helps,
Robi

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Robi Bhattacharjee

Expertise

I can answer a variety of questions on mathematics. Questions on trigonometry, calculus(preferably single variable), algebra, geometry, and number theory will be answered. I cannot answer questions on abstract branches of mathematics such as group theory. I also cannot answer questions on statistics. In number theory, I can answer questions on congruences, prime numbers, units, functions, and the riemann-zeta function.

Experience

I have studied advanced math my entire life. I started calculus in sixth grade. I have attended numerous math competitions and I am attending math organizations such as the San-Diego math circle. Also, this year I have been invited to the USAMO which is a prestigious math competition (Every year the USAMO invites 500 students from across the USA to participate in this competition. The top 6 go to represent the USA in the International Math Olympiad).

Organizations
I am in the San Diego Math Circle

Education/Credentials
I am entering high school and have received a perfect score and the STAR test 5 times in a row. I also have gotten recognitions in the AMC 10, AIME, Math Counts, and ARML. Additionally, I have won the San Diego Math Olimpiad twice in a row.

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