The average of 30 numbers is 40 and that of other 40 numbers is 30. The average

Question

The average of 30 numbers is 40 and that of other 40 numbers is 30. The average of all the numbers is

Options:

A . 34

B . 34.5

C . 35

D . 34$2/7$

Answer: Option D
Answer: (d)Average of all numbers= ${30×40+40×30}/70$= $240/7$ = 34$2/7$Aliter : Using Rule 10, Here, $n_1$ = 30, $a_1$ = 40 $n_2$ = 40, $a_2$ = 30 ∴ Average = ${n_1a_1+ n_2a_2}/{n_1+ n_2}$

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