Average age of 17 student of a class is 16 years. If a new student join the class then average age becomes 20. Then find 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 17 students.
The average age of the 17 students is given as 16 years. The formula for average is:

\[ \text{Average} = \frac{\text{Total Age}}{\text{Number of Students}} \]

From this, we can rearrange the formula to find the total age:

\[ \text{Total Age} = \text{Average} \times \text{Number of Students} \]

Substituting the values:

\[ \text{Total Age} = 16 \times 17 = 272 \text{ years} \]

### Step 2: Calculate the total age of the 18 students after the new student joins.
After the new student joins, the average age becomes 20 years for 18 students. Using the same formula:

\[ \text{Total Age} = \text{Average} \times \text{Number of Students} \]

Substituting the new values:

\[ \text{Total Age} = 20 \times 18 = 360 \text{ years} \]

### Step 3: Find the age of the new student.
To find the age of the new student, we can subtract the total age of the original 17 students from the total age of the 18 students:

\[ \text{Age of New Student} = \text{Total Age of 18 Students} - \text{Total Age of 17 Students} \]

Substituting the values we calculated:

\[ \text{Age of New Student} = 360 - 272 = 88 \text{ years} \]

### Final Answer:
The age of the new student is **88 years**.

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