00:01
So what do we know here, right? we are asked about the price elasticity of demand along the demand curve with a constant slope.
00:08
So we have quantity and price.
00:12
We have a linear demand curve, right, constant slope.
00:15
And that slope is, of course, negative.
00:18
So let's think about elasticity.
00:20
Elasticity is the percentage change in quantity over the percentage change in price.
00:25
This is equal to the change in quantity over the baseline quantity.
00:30
Over the change in price times the price because that's just the definition of a percentage change, right? the change over the reference level.
00:39
So this is equal to the change in quantity over the change in price times price over quantity.
00:48
But remember that the slope of this demand curve is the change in price over the quantity.
00:55
Do you see how these things are related, right? they're the same, they're just the reverse of each other...