Intermediate Microeconomics · free preview

Derivatives as Marginal Quantities

The derivative is the instant rate of change, and economics reads it as a marginal quantity, the extra output, cost or utility of one more unit, which turns prose arguments into computable ones.

1. Rate of change made precise

Rate of change made precise

2. A production example

A production example

3. From marginal products to marginal cost

From marginal products to marginal cost

4. Reading a tangent correctly

Reading a tangent correctly

5. The definition in words

What exactly does the derivative f′(x)f'(x) measure about a function ff at the point xx?

6. Marginal product at eight

The workshop's output is f(x)=20x−x2f(x) = 20x - x^2. What is the marginal product of labor at x=8x = 8?

7. Where output peaks

Total output is f(x)=20x−x2f(x) = 20x - x^2. At what xx does output reach its maximum, and why?

8. Marginal cost from marginal product

Labor costs 2 dollars per unit and the marginal product of labor at the current input is 5. What is the marginal cost of output near that point?

9. The slope of the tangent

For f(x)=20x−x2f(x) = 20x - x^2, compute the derivative f′(5)f'(5), and write the number.

10. Output at the point

For the same workshop function f(x)=20x−x2f(x) = 20x - x^2, compute total output f(5)f(5), and write the number.

11. Marginal product at eight workers

For the workshop output f of x equals 20x minus x squared, what is the marginal product at 8 workers?

12. The peak of output

At what labor level does the workshop's total output reach its maximum?

13. Marginal cost from productivity

With labor at 2 dollars per unit, what is the workshop's marginal cost near 5 workers?

14. Negative marginal product

What does f prime of 12 equal to minus 4 tell the workshop?

15. Where the margin hits twelve

The marginal product is 20 minus 2x. Find the worker level where it equals 12, and write the number.

16. The exchange rate to cost

Near 5 workers one more unit of output needs one tenth of a worker. Compute its cost at 2 dollars per worker and write it in decimals.

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