Question

find the mean of the first six multiple of 3

Answer 1

$\huge\mathfrak{Answer \ :-}$

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Answer 2

Mean =( 3 + 6 + 9 + 12 + 15 + 18)/6

.................................................................................................................

3+6.........+18

= 3( 1+2+.....+6)

= 3 ( 6 x 7/2)              using n ( n+1)/2

= 3 x 21

so

Mean = 3 x 21/6 = 21/2 = 10.5