If out of 10 selected students for an examination, 3 were of 20 years, age, 4 of 21 and 3 of 22 years, the average age of the group is:

Options

A. 22 years
B. 21 years
C. 21.5 years
D. 20 years

Answer

To find the average age of the group of students, we will follow these steps:

### Step 1: Calculate the total age for each group of students.
- For the 3 students who are 20 years old:
\[ \text{Total age} = 3 \times 20 = 60 \]

- For the 4 students who are 21 years old:
\[ \text{Total age} = 4 \times 21 = 84 \]

- For the 3 students who are 22 years old:
\[ \text{Total age} = 3 \times 22 = 66 \]

### Step 2: Calculate the overall total age of all students.
Now, we sum up all the total ages calculated in Step 1:
\[ \text{Total age of all students} = 60 + 84 + 66 \]
Calculating this gives:
\[ 60 + 84 = 144 \]
\[ 144 + 66 = 210 \]

### Step 3: Calculate the average age.
The average age is calculated by dividing the total age by the number of students:
\[ \text{Average age} = \frac{\text{Total age}}{\text{Number of students}} = \frac{210}{10} \]
Calculating this gives:
\[ \frac{210}{10} = 21 \]

### Final Answer:
The average age of the group is **21 years**.

---