The average expenditure of 4 Boys and 3 Girls is Rs. 120 . If the average expenditure of Boy's is Rs. 150 then find out average expenditure of Girl's.

Answer

To solve the problem step by step, we can follow these steps:

### Step 1: Understand the given information
We know that:
- The average expenditure of 4 boys and 3 girls is Rs. 120.
- The average expenditure of the boys is Rs. 150.

### Step 2: Calculate the total expenditure of 4 boys and 3 girls
The average expenditure of 4 boys and 3 girls is given as Rs. 120. Since there are a total of 7 individuals (4 boys + 3 girls), we can calculate the total expenditure (TE) using the formula for average:

\[ \text{Average} = \frac{\text{Total Expenditure}}{\text{Number of Individuals}} \]

Thus, we can rearrange this to find the total expenditure:

\[ \text{Total Expenditure} = \text{Average} \times \text{Number of Individuals} \]

Substituting the values:

\[ \text{Total Expenditure} = 120 \times 7 = 840 \]

### Step 3: Calculate the total expenditure of the boys
We know the average expenditure of the boys is Rs. 150. Therefore, we can calculate the total expenditure of the boys (TE_boys) using the same formula:

\[ \text{Total Expenditure of Boys} = \text{Average Expenditure of Boys} \times \text{Number of Boys} \]

Substituting the values:

\[ \text{Total Expenditure of Boys} = 150 \times 4 = 600 \]

### Step 4: Calculate the total expenditure of the girls
Now, we can find the total expenditure of the girls (TE_girls) by subtracting the total expenditure of the boys from the total expenditure of all individuals:

\[ \text{Total Expenditure of Girls} = \text{Total Expenditure} - \text{Total Expenditure of Boys} \]

Substituting the values:

\[ \text{Total Expenditure of Girls} = 840 - 600 = 240 \]

### Step 5: Calculate the average expenditure of the girls
Finally, we can find the average expenditure of the girls (AE_girls) using the formula:

\[ \text{Average Expenditure of Girls} = \frac{\text{Total Expenditure of Girls}}{\text{Number of Girls}} \]

Substituting the values:

\[ \text{Average Expenditure of Girls} = \frac{240}{3} = 80 \]

### Conclusion
The average expenditure of the girls is Rs. 80.

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