A man makes 60 articles in the 1st hour. His efficiency decreases by 25% in the 2nd hour, increases by 40% in the 3rd hour, decreases by 33% in the 4th hour and increases by 50% in the 5th hour. If he has to work for more than 1 hour, then in which hour the average number of articles produced per hour then would be minimum ?

Options

A. 2nd hour
B. After 5th hour
C. 3rd hour
D. 2nd and 4th hour both

Answer

To solve the problem step by step, we will calculate the number of articles produced by the man in each hour based on the given efficiencies, and then determine in which hour the average number of articles produced per hour is minimum.

### Step 1: Calculate the number of articles produced in each hour.

1. **First Hour:**
- Articles produced = 60

2. **Second Hour:**
- Efficiency decreases by 25%.
- Articles produced = 60 - (25% of 60) = 60 - 15 = 45

3. **Third Hour:**
- Efficiency increases by 40% from the second hour.
- Articles produced = 45 + (40% of 45) = 45 + 18 = 63

4. **Fourth Hour:**
- Efficiency decreases by 33% from the third hour.
- Articles produced = 63 - (33% of 63) = 63 - 21 = 42

5. **Fifth Hour:**
- Efficiency increases by 50% from the fourth hour.
- Articles produced = 42 + (50% of 42) = 42 + 21 = 63

### Summary of Articles Produced:
- 1st hour: 60 articles
- 2nd hour: 45 articles
- 3rd hour: 63 articles
- 4th hour: 42 articles
- 5th hour: 63 articles

### Step 2: Calculate the average number of articles produced per hour.

To find the average, we sum the articles produced in each hour and divide by the number of hours worked.

Total articles produced = 60 + 45 + 63 + 42 + 63 = 273

Average articles produced per hour = Total articles / Number of hours
= 273 / 5 = 54.6

### Step 3: Determine in which hour the average number of articles produced per hour is minimum.

Now we need to compare the articles produced in each hour to the average:

- 1st hour: 60 (greater than 54.6)
- 2nd hour: 45 (less than 54.6)
- 3rd hour: 63 (greater than 54.6)
- 4th hour: 42 (less than 54.6)
- 5th hour: 63 (greater than 54.6)

The hours where the production is less than the average (54.6) are the 2nd hour (45 articles) and the 4th hour (42 articles).

Among these, the minimum production occurs in the 4th hour (42 articles).

### Conclusion:
The hour in which the average number of articles produced per hour is minimum is the **4th hour**.

---