The average height of 20 boys is 120 cm and the average height of 10 girls is 117 cm. Find the average height of these 30 students.

Answer

To find the average height of the 30 students (20 boys and 10 girls), we can follow these steps:

### Step 1: Calculate the total height of the boys
The average height of the boys is given as 120 cm, and there are 20 boys.

Total height of boys = Average height of boys × Number of boys
Total height of boys = 120 cm × 20 = 2400 cm

### Step 2: Calculate the total height of the girls
The average height of the girls is given as 117 cm, and there are 10 girls.

Total height of girls = Average height of girls × Number of girls
Total height of girls = 117 cm × 10 = 1170 cm

### Step 3: Calculate the total height of all students
Now, we can find the total height of all 30 students by adding the total height of boys and girls.

Total height of all students = Total height of boys + Total height of girls
Total height of all students = 2400 cm + 1170 cm = 3570 cm

### Step 4: Calculate the average height of all students
To find the average height of all 30 students, we divide the total height by the total number of students.

Average height = Total height of all students / Total number of students
Average height = 3570 cm / 30 = 119 cm

### Final Answer
The average height of the 30 students is **119 cm**.

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