The average of 30 results is 20 and the average of other 20 results is 30. What

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The average of 30 results is 20 and the average of other 20 results is 30. What is the average of all the results ?

Options:

A . 25

B . 50

C . 48

D . 24

Answer: Option D
Answer: (d)Using Rule 10, If the average of '$n_1$' numbers is $a_1$ and the average of '$n_2$' numbers is $a_2$, then average of total numbers $n_1$ and $n_2$ is$Average = {n_1a_1 + n_2a_2}/{n_1 + n_2}$ Required average= ${20×30+20×30}/{30+20}$= ${600+600}/50$= $1200/50$ = 24

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