<p>Given the demand function: $$Q(P)=600-2P$$ The consumer surplus is the area under the demand curve  above the equilibrium price $P^*$ or algebraically;
$$\int_{0}^{P^*}Q(P)\text{dP}$$
The change in consumer surplus as a result of price change from $P_0^*$ to $P_1^*$ is then:
$$\begin{align*}\Delta CS&amp;=&amp;
\int_{P_1^*}^{P_0^*}Q(P)\text{dP}\\
\end{align*}$$ </p>

CC BY-SA 3.0
2015-05-21T19:28:06.787Z
the policy here is that, on homework-style questions, the full answer should not be given, but only a few hints.
VicAche
CC BY-SA 3.0
2015-05-21T14:37:05.027Z
2015-05-21T23:52:24.590Z
2015-05-21T23:52:24.590Z
Dreyfus
<p><img src="https://i.sstatic.net/7jyya.png" alt="enter image description here"></p>

<p>Image courtesy <a href="http://economicsonline.co.uk/" rel="nofollow noreferrer">http://economicsonline.co.uk/</a></p>

<p>Consumer surplus is the sum (integral) of differences between the price each consumer would have payed and the price they got to pay. You need to find out the area of the green zone on the above graph, in the case of your model.</p>

CC BY-SA 3.0
2015-05-20T16:07:08.260Z
2015-05-20T16:07:08.260Z
VicAche
<p>The demand for rail travel is $Q^d = 600 - 2P$ where quantity is thousands of train journeys per quarter and $P$ is in £ per journey. How much would the consumer surplus change if rising cost of electricity led the train companies to raise price from £70 to £100. </p>

<p>Calculating the choke price, $600 = 2P$. Thefore $P = 300$.</p>

<p>At £70, $Q^d = 460$. Therefore Consumer surplus is $(460-300)/2*460 = £36,800$</p>

<p>At £100, $Q^d = 400$. Therefore consumer surplus is $(400-300)/2*400 = £20,000$</p>

<p>Difference is $£16,800$.</p>

<p>I've got the answer wrong, but i'm sure where, any help is appreciated. </p>

<microeconomics><consumer-surplus>
Consumer Surplus question
24Aj1990
# Consumer Surplus question

(Asked by: username_0 on 2015-05-20)

The demand for rail travel is $Q^d = 600 - 2P$ where quantity is thousands of train journeys per quarter and $P$ is in £ per journey. How much would the consumer surplus change if rising cost of electricity led the train companies to raise price from £70 to £100.

Calculating the choke price, $600 = 2P$. Thefore $P = 300$.

At £70, $Q^d = 460$. Therefore Consumer surplus is $(460-300)/2\*460 = £36,800$

At £100, $Q^d = 400$. Therefore consumer surplus is $(400-300)/2\*400 = £20,000$

Difference is $£16,800$.

I've got the answer wrong, but i'm sure where, any help is appreciated.

**Tags:** microeconomics, consumer-surplus

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## 2 answers

### Answer by username_2 on 2015-05-20. Score: 3 | Accepted answer

![enter image description here](https://i.sstatic.net/7jyya.png)

Image courtesy <http://economicsonline.co.uk/>

Consumer surplus is the sum (integral) of differences between the price each consumer would have payed and the price they got to pay. You need to find out the area of the green zone on the above graph, in the case of your model.


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### Answer by username_1 on 2015-05-21. Score: 1

Given the demand function: $$Q(P)=600-2P$$ The consumer surplus is the area under the demand curve above the equilibrium price $P^\*$ or algebraically;
$$\int\_{0}^{P^\*}Q(P)\text{dP}$$
The change in consumer surplus as a result of price change from $P\_0^\*$ to $P\_1^\*$ is then:
$$\begin{align\*}\Delta CS&=&
\int\_{P\_1^\*}^{P\_0^\*}Q(P)\text{dP}\\
\end{align\*}$$

> **Comments:**
> **username_2**: the policy here is that, on homework-style questions, the full answer should not be given, but only a few hints.  

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