Average age of 10 students of a class is 18 years. If one more student join them now , the average becomes 19 years .What is the age of new student ?

Answer

To find the age of the new student who joins the class, we can follow these steps:

### Step 1: Calculate the total age of the original 10 students.
The average age of the 10 students is 18 years. To find the total age of these students, we use the formula:
\[ \text{Total Age} = \text{Average Age} \times \text{Number of Students} \]
So, the total age of the 10 students is:
\[ \text{Total Age} = 18 \times 10 = 180 \text{ years} \]

### Step 2: Calculate the total age of the 11 students after the new student joins.
After the new student joins, the average age of the 11 students becomes 19 years. Again, we use the formula for total age:
\[ \text{Total Age of 11 students} = \text{New Average Age} \times \text{Number of Students} \]
Thus, the total age of the 11 students is:
\[ \text{Total Age of 11 students} = 19 \times 11 = 209 \text{ years} \]

### Step 3: Find the age of the new student.
To find the age of the new student, we subtract the total age of the original 10 students from the total age of the 11 students:
\[ \text{Age of New Student} = \text{Total Age of 11 students} - \text{Total Age of 10 students} \]
Substituting the values we calculated:
\[ \text{Age of New Student} = 209 - 180 = 29 \text{ years} \]

### Final Answer:
The age of the new student is **29 years**.

---