The average age of 9 girls is 16 years. The average age of 11 boys is 26 years. What is the average age of all these boys and girls taken together?

22 years 23 years 22.5 years 21.5 years

21.5 years

Sum of age of 9 girls = 9 × 16 = 144 years Sum of age of 11 boys is = 11 × 26 = 286 years Average of all boys and girls together = \(\frac{144 + 286 }{20}\)  = \(\frac{430}{20}\) = 21.5 years