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The question asks to find the average weight of two new students joining a class, given the following details:

- The current average weight of 20 students in the class is 45 kg.
- Two new students with weights \(x \, \text{kg}\) and \(x+4 \, \text{kg}\) join the class.
- The new average weight of the class increases by 1 kg (i.e., it becomes 46 kg).

We can break it down step by step:

1. **Total weight of the initial 20 students**:  
   Since the average weight is 45 kg, the total weight of these 20 students is:
   \[
   20 \times 45 = 900 \, \text{kg}
   \]

2. **Total weight after two students join**:  
   The new average weight is 46 kg, and the total number of students becomes \(20 + 2 = 22\). So the total weight of the 22 students is:
   \[
   22 \times 46 = 1012 \, \text{kg}
   \]

3. **Weight of the two new students**:  
   The total weight of the two new students can be found by subtracting the initial total weight (900 kg) from the new total weight (1012 kg):
   \[
   \text{Weight of the two students} = 1012 - 900 = 112 \, \text{kg}
   \]

4. **Setting up the equation for the two new students**:  
   The weights of the two students are \(x \, \text{kg}\) and \(x+4 \, \text{kg}\). So:
   \[
   x + (x + 4) = 112
   \]
   Simplifying:
   \[
   2x + 4 = 112
   \]
   \[
   2x = 108
   \]
   \[
   x = 54
   \]

5. **Average weight of the two new students**:  
   The weights are \(x = 54 \, \text{kg}\) and \(x+4 = 58 \, \text{kg}\). Their average weight is:
   \[
   \frac{54 + 58}{2} = \frac{112}{2} = 56 \, \text{kg}
   \]

So, the average weight of the two new students is **56 kg**.

Let me know if you have any questions, or if you'd like further explanation. Here are five related questions to practice with:

1. What happens to the average weight of a class if a new student with a weight lower than the current average joins?
2. How would the total weight calculation change if the class originally had 30 students?
3. If the two new students had different weight differences, how would you adjust the formula?
4. What if the average weight of the new class had only increased by 0.5 kg instead of 1 kg?
5. How would you solve this if the weight change caused a decrease in the average?

**Tip**: When solving average-based problems, always focus on the relationship between total sums and the number of elements.

The average weight of 20 students in a class is 45 kg. If two students whose weights are x kg and (x + 4) kg joined the class, then the average weight of the class is increased by 1 kg. Find the average weight of the two new students.

Solve this algebra problem about averages. Given the average weight of 20 students is 45 kg, determine the average weight of two new students whose weights are x kg and (x + 4) kg. Learn to calculate averages and use algebraic equations to find the solution.

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