The average weight of a boat crew of 8 men is 74 KG. A man weighing 72 kg is replaced by one weighing 80 kg. Find the new average.

The initial average weight of the crew of 8 men is given as 74 kg. 

1. **Calculate the initial total weight**:
   \[
   \text{Total weight} = \text{Average weight} \times \text{Number of men} = 74 \times 8 = 592 \text{ kg}
   \]

2. **Adjust for the replacement**:
   - A man weighing 72 kg is replaced by another man weighing 80 kg.
   - The increase in weight is:
     \[
     80 - 72 = 8 \text{ kg}
     \]

3. **Find the new total weight**:
   \[
   \text{New total weight} = 592 + 8 = 600 \text{ kg}
   \]

4. **Calculate the new average**:
   \[
   \text{New average} = \frac{\text{New total weight}}{\text{Number of men}} = \frac{600}{8} = 75 \text{ kg}
   \]

### Answer:
The new average weight of the boat crew is **75 kg**.

Would you like further explanation or have any questions?

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Here are five additional questions that expand on this topic:

1. If two more men join the crew, each weighing 78 kg, what would the new average weight be?
2. How much would the average change if the replacement man weighed 70 kg instead of 80 kg?
3. What would the new average be if three men were each replaced by heavier individuals adding a total of 15 kg to the original weight?
4. How would the calculation change if the initial crew had an unknown average?
5. What is the effect on the average if the replaced member weighs exactly the same as his replacement?

**Tip**: In average-related problems, changing one or more individual values affects the total sum, and hence the average recalculations depend on changes in the total.

Learn how to calculate the new average weight of a boat crew after replacing one member. This step-by-step solution explains key arithmetic concepts, including averages and weight adjustments. Perfect for students in Grades 5-7.

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