The average age of 30 girls is 13 yr. The average of first 18 girls is 15 yr. Find out the average age of remaining 12 girls.
Correct Answer: 10yr
Explanation:
Total age of 30 girls = 30 x 13 = 390 yr
Total age of 18 girls = 18 x 15 = 270 yr.
∴ Age of remaining 12 girls = 390 - 270 = 120 yr
∴ Required average = 120/12 = 10 yr
