Question

The average of six number is $12$ and The average of $4$ numbers is $15$ what is the average of these $10$ number?

Answer 1

Let the Sum of first 6 numbers be S

So, $\frac{S}{6}=12\Rightarrow S=72$

and the Sum of next 4 numbers be T

So, $\frac{T}{4}=15\Rightarrow T=60$

Average of ten numbers will be $=\frac{S+T}{10}=\frac{60+72}{10}=13.2$