Supply and demand functions for butter pecan ice cream

[gillgill]

Let supply and demand functions for butter pecan ice cream given by
p=S(q)= 2/5q and p=D(q)=100 - 2/5q
where p is the price in dollars and q is the number of 10-gallon tubs.
Find the equilibrium quantity and the equilibrium price.
do i just set them equal to each other??

2/5q=100-2/5q
equilibrium q=125
equilibrium p=50
are these answers correct?

 

[HallsofIvy]

Yes, they are correct.

You didn't really need someone to tell you that did you? Just put p= 50,q= 125 into the equations and see if they are correct:
p= (2/5)q= (2/5)(125)= 2(25)= 50 is correct and
p= 100- (2/4)q= 100- 50= 50 is correct.

 

[gillgill]

coz someone told me that they are not correct...so i just want to make sure...
thanks...i have another question
Suppose a cost-benefit model is given by
y=(6.5x)/(102-x)
where y is the cost in thousands of dollars of removing x percent of a certian pollutant.
a) find the cost of removing each percent of pollutants:
0%, 80%, 100%
do i just sub in 0, 0.8 and 1 in the equation where it has x?? or u sub in 1, 80 and 100?