<p>Sorry for asking such a silly question, but something seems odd about my answer to this question: </p>

<blockquote>
  <p>Suppose that two consumers, Jeff and Walt, are the only consumers in the market for carrots.  Jeff’s demand curve is given by $Q_{Jeff}=10-2P$ and Walt’s demand curve is given by $Q_{Walt}=15-3P$.</p>
  
  <p>a) Find the market demand curve for carrots.</p>
  
  <p>b) Suppose the market supply curve is given by $Q_S = 2P$.  Find the market equilibrium price and quantity.</p>
</blockquote>

<p>So, this is how I answered the question:</p>

<blockquote>
  <p>(a)
  Let $Q_{Jeff} = 10 – 2P$ and $Q_{Walt} = 15 – 3P$. Then, $Q_{Jeff} + Q_{Walt} = Q_D = (10 – 2P) + (15 – 3P) = 10 + 15 – 2P – 3P = 25 – 5P$. Therefore, the demand curve for carrots is $Q_D(P) = 25 – 5P$.</p>
  
  <p>(b)
    Let $Q_S = 2P$ and $Q_D = 25 – 5P$. At the market equilibrium price:
    $$2P = 25 – 5P
\implies 2P + 5P = 25
\implies 7P = 25
\implies P = 25/7.$$
  Thus, $P_E = 25/7$. Hence, $Q_E = 2P = 2(25/7) = 50/7$.</p>
</blockquote>

<p>I guess I just wasn't expecting fractions in my answer. As far as I can tell, I did everything right. Did I screw up somewhere?</p>

CC BY-SA 3.0
2015-10-09T04:41:14.850Z
This looks quite fine. You did well!
Kitsune Cavalry
CC BY-SA 3.0
2015-10-09T13:17:28.413Z
Your solution is right. There could be always fractions for demand, supply quantities and for price.
optimal control
CC BY-SA 3.0
2015-10-09T16:16:17.087Z
Okay, thanks folks. I actually realised the odd feeling was a result of me using a proof-like method when my first-year economics class apparently calls for drawing the curves and adding them horizontally. I tried that method and got the same answer, so I suppose it must be probably right.
ConJoJohn
CC BY-SA 3.0
2016-09-23T06:52:04.713Z
I'm voting to close this question as off-topic because it was not really a question, more of an affirmation request.
Giskard
CC BY-SA 3.0
2017-07-04T09:33:02.747Z
@denesp what happened to this vote?
luchonacho
CC BY-SA 3.0
2017-07-04T11:24:57.257Z
@luchonacho Looks like it did not reach 5 votes need to close.
Giskard
CC BY-SA 3.0
2017-07-04T18:21:20.683Z
I'm voting to close this question as off-topic because it was not really a question, but a confirmation of results. This is never going to be of use to any other user.
luchonacho
<supply-and-demand><markets>
Did I do something wrong in calculating the market equilibrium?
ConJoJohn
# Did I do something wrong in calculating the market equilibrium?

(Asked by: username_0 on 2015-10-09)

Sorry for asking such a silly question, but something seems odd about my answer to this question:

> Suppose that two consumers, Jeff and Walt, are the only consumers in the market for carrots. Jeff’s demand curve is given by $Q\_{Jeff}=10-2P$ and Walt’s demand curve is given by $Q\_{Walt}=15-3P$.
>
> a) Find the market demand curve for carrots.
>
> b) Suppose the market supply curve is given by $Q\_S = 2P$. Find the market equilibrium price and quantity.

So, this is how I answered the question:

> (a)
> Let $Q\_{Jeff} = 10 – 2P$ and $Q\_{Walt} = 15 – 3P$. Then, $Q\_{Jeff} + Q\_{Walt} = Q\_D = (10 – 2P) + (15 – 3P) = 10 + 15 – 2P – 3P = 25 – 5P$. Therefore, the demand curve for carrots is $Q\_D(P) = 25 – 5P$.
>
> (b)
> Let $Q\_S = 2P$ and $Q\_D = 25 – 5P$. At the market equilibrium price:
> $$2P = 25 – 5P
> \implies 2P + 5P = 25
> \implies 7P = 25
> \implies P = 25/7.$$
> Thus, $P\_E = 25/7$. Hence, $Q\_E = 2P = 2(25/7) = 50/7$.

I guess I just wasn't expecting fractions in my answer. As far as I can tell, I did everything right. Did I screw up somewhere?

**Tags:** supply-and-demand, markets

> **Comments:**
> **username_1**: This looks quite fine. You did well!  
> **username_2**: Your solution is right. There could be always fractions for demand, supply quantities and for price.  
> **username_0**: Okay, thanks folks. I actually realised the odd feeling was a result of me using a proof-like method when my first-year economics class apparently calls for drawing the curves and adding them horizontally. I tried that method and got the same answer, so I suppose it must be probably right.  
> **username_3**: I'm voting to close this question as off-topic because it was not really a question, more of an affirmation request.  
> **username_4**: @denesp what happened to this vote?  
> **username_3**: @username_4 Looks like it did not reach 5 votes need to close.  
> **username_4**: I'm voting to close this question as off-topic because it was not really a question, but a confirmation of results. This is never going to be of use to any other user.  

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## 0 answers

