The mean weight of 15 boys is 43 kg. If two boys with weights 34 kg and 35 kg join them, fin the new mean weight.

Answer

To find the new mean weight after two boys join the group, follow these steps:

### Step 1: Calculate the total weight of the initial group of boys.
The mean weight of the 15 boys is given as 43 kg. The formula for mean is:

\[ \text{Mean} = \frac{\text{Total Weight}}{\text{Number of Boys}} \]

Rearranging this formula gives us:

\[ \text{Total Weight} = \text{Mean} \times \text{Number of Boys} \]

Substituting the known values:

\[ \text{Total Weight} = 43 \, \text{kg} \times 15 = 645 \, \text{kg} \]

### Step 2: Add the weights of the two new boys.
The weights of the two new boys are 34 kg and 35 kg. We add these weights to the total weight calculated in Step 1:

\[ \text{New Total Weight} = 645 \, \text{kg} + 34 \, \text{kg} + 35 \, \text{kg} = 714 \, \text{kg} \]

### Step 3: Calculate the new total number of boys.
The initial number of boys is 15, and with the addition of 2 new boys, the new total number of boys is:

\[ \text{New Number of Boys} = 15 + 2 = 17 \]

### Step 4: Calculate the new mean weight.
Using the new total weight and the new number of boys, we can find the new mean weight:

\[ \text{New Mean Weight} = \frac{\text{New Total Weight}}{\text{New Number of Boys}} = \frac{714 \, \text{kg}}{17} \]

Calculating this gives:

\[ \text{New Mean Weight} = 42 \, \text{kg} \]

### Final Answer:
The new mean weight of the boys is **42 kg**.

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