The third phase is where MP is negative.

Question 49

HardOriginal question

Capital is fixed and labour is varied. The table shows total product.

Labour (units)	1	2	3	4	5	6	7	8	9
Total product	10	24	39	52	60	66	70	70	63

The third phase is where MP is negative. From which unit of labour does it begin?

The 8th unit, where MP is zeroCorrect answerYour answerThe 4th unit, where MP starts fallingCorrect answerYour answerThe 5th unit, where AP starts fallingCorrect answerYour answerThe 9th unit, where MP becomes negativeCorrect answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer D

Correct answer: D

The third phase is where TP falls, i.e. MP is negative.
TP falls from 70 to 63 at the 9th unit (MP = −7).

Worth noting

At the 8th unit MP is exactly zero: that is the end of the second phase, where TP peaks.

Concept: Start of the third phase
Typical timeTypical: 100 s
Your timeYours: —

The rule this testsThe law of variable proportions

Practise this chapter →

Ten questions from Production Function: TP, MP and AP, at your own pace.

Practise this chapter →

Ten questions from Production Function: TP, MP and AP, at your own pace.

The third phase is where MP is negative.

Question 49

Explanation