Question

Calculate the consumer surplus for the demand function
P = 50 − 4Q
when the market price is P = 10.

Answer 1

P = 50 - 4Q
10 = 50 - 4Q
rearranging we get:
4Q = 50 - 10
4Q = 40
Q = 10

Answer 2

P = 50 - 4Q

P = 10

Plug in 10 for 'P':

10 = 50 - 4Q

Subtract 50 to both sides:

-40 = -4Q

Divide -4 to both sides:

Q = 10