Point Price Elasticity of Demand = (% change in Quantity)/(% change in Price)

Point Price Elasticity of Demand = (P/Q)(∆Q/∆P)

Where (∆Q/∆P) is the derivative of the demand function with respect to P. You don’t really need to take the derivative of the demand function, just find the coefficient (the number) next to Price (P) in the demand function and that will give you the value for ∆Q/∆P because it is showing you how much Q is going to change given a 1 unit change in P. Finding the point elasticity solution is best demonstrated with examples...

**Example 1:**

**To find the point price elasticity of demand we begin with an example demand curve:**

Q = 15,000 - 50P

Imagine that given this demand curve we are asked to figure out what the point
price elasticity of demand is at two different prices, P = 100 and P = 10.

First we need to obtain the derivative of the demand function when it's expressed with Q as a function of P. Since quantity (Q) goes down by 50 each time price (P) goes up by 1,

This gives us (∆Q/∆P)= -50

Next we need to find the quantity demanded at each
associated price and pair it together with the price: (100; 10,000), (10; 14,500)

Then we plug those values into our point elasticity of demand formula to obtain the following:

e = -50(100/10,000) = -.5

e = -50(10/14,500) = -.034

Then we plug those values into our point elasticity of demand formula to obtain the following:

e = -50(100/10,000) = -.5

e = -50(10/14,500) = -.034

And these results make sense, first, because they are
negative (which demonstrates a downward sloping demand relationship) and second, because the higher level results
in a relatively more elastic price elasticity of demand measure.

**Example 2:**

How to find the point price elasticity of demand with the
following demand function:

Q = 4,000 – 400P

We know that ∆Q/∆P in this problem is -400, and we need to
find the point price elasticity of demand at a price of 10 and at a price of 8.

At a price of ten, we demand 0 of the good, so the measure
is undefined. At a price of 8 we will
demand 400 of the good, so the associated measure is:

e = -400(8/400) = -8

**Example 3:**

What about a demand function of:

Q = 8,800 – 1,000P

Here our ∆Q/∆P will be -1,000 and we will need to find the
associated measure at prices of 0, 2, 4, and 6.

This means we will end up with:

e = -1,000(0/8,800) = 0

e = -1,000(2/6,800) = -0.294

e = -1,000(4/4,800) = -0.8333

e = -1,000(6/2,800) = -2.14

Sometimes you may be required to solve for quantity or price and are given a point price elasticity of demand measure. In this case you need to backwards solve by rearranging the point price elasticity of demand formula to get the quantity or price you need for the problem.

Sometimes you may be required to solve for quantity or price and are given a point price elasticity of demand measure. In this case you need to backwards solve by rearranging the point price elasticity of demand formula to get the quantity or price you need for the problem.

**Summary:****The trick to solving point price elasticity of demand problems is to find the coefficient on the price (P) and then to plug the corresponding price and quantity values in to the point price elasticity of demand formula. After that you can simplify using algebra.**

shouldn't quantity demanded what price equals 8 be 4000 - 3200 equals 800.

ReplyDeleteYes, you are right! the equations should be adjusted to include 800 instead of 400 (but the methods/calculations are all correct except this).

ReplyDeleteYou shared your post here how to calculate price.Thanks for your post.

ReplyDeletepoint to point

very nice article

ReplyDeleteHelpful for elasticity of demand at a point

ReplyDeleteThank you

ReplyDeleteWhy isn't the ∆Q/∆P = (1/slope) = (1/ -50) ??

ReplyDeleteLittle Tommy spends all of his weekly allowance ($20) on Swiss Chocolate and toy cars. Chocolates are $1 each while toy cars are $5 each.

ReplyDeletePlot Tommy’s budget line.

What happens to Tommy’s budget line if the price of chocolate rises to $2? If his allowance rises to $30?

help

Good work done

ReplyDeleteSuppose the question asks you, say, what is the elasticity when price changes from 10 to 20? Do you average the two elasticity estimates at the start and endpoint? Or do you have to use the cumbersome midpoint method?

ReplyDeletefind the price elasticity of demand for demand function x =100e^(-p/200) at p= rs. 200

ReplyDeleteThanks for the informative article. This is one of the best resources I have found in quite some time. Nicely written and great info. I really cannot thank you enough for sharing...

ReplyDeleteOracle DBA Online Training

This is an awesome post. Really very informative and creative contents. This concept is a good way to enhance knowledge. I like it and help me to development very well. Thank you for this brief explanation and very nice information. Well, got good knowledge.

ReplyDeleteSql server dba online training

Hi, Great.. Tutorial is just awesome..It is really helpful for a newbie like me.. I am a regular follower of your blog. Really very informative post you shared here. Kindly keep blogging.

ReplyDeletemsbi online training

The site was so nice, I found out about a lot of great things. I like the way you make your blog posts. Keep up the good work and may you gain success in the long run.

ReplyDeleteReactJS Online Training

I appreciate your efforts because it conveys the message of what you are trying to say. It's a great skill to make even the person who doesn't know about the subject could able to understand the subject . Your blogs are understandable and also elaborately described. I hope to read more and more interesting articles from your blog. All the best.

ReplyDeleteTableau online training