# Did I do something wrong in calculating the market equilibrium?

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?

• This looks quite fine. You did well! – Kitsune Cavalry Oct 9 '15 at 4:41
• Your solution is right. There could be always fractions for demand, supply quantities and for price. – optimal control Oct 9 '15 at 13:17
• 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 Oct 9 '15 at 16:16
• I'm voting to close this question as off-topic because it was not really a question, more of an affirmation request. – Giskard Sep 23 '16 at 6:52
• 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 Jul 4 '17 at 18:21