The average of the first five multiples of 9 is:
A. 20
B. 27
C. 28
D. 30
Answer: Option B
Solution(By Examveda Team)
$$\eqalign{ & {\text{Required}}\,{\text{average}} \cr & = {\frac{{{\text{total}}\,{\text{sum}}\,{\text{of}}\,{\text{multiple}}\,{\text{of}}\,9}}{5}} \cr & = {\frac{{9 + 18 + 27 + 36 + 45}}{5}} \cr & = 27 \cr} $$Note that, average of 9 and 45 is also 27.
And average of 18 and 36 is also 27.
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Comments ( 9 )
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nice
(Fist9+last 45)/2=27
9,18,27.36,45
Avg = 1st + Last / 2
(9+45)/2 = 27
RJ Champ
Ans = 9(1+2+3+4+5)/5
(1st +last term) / 2
(9+45) / 2
= 54/2
=27
9(1,2,3,4,5)/5 = 9*5(5+1)/2/5 9*6/2
Another method for this ,
Avg= first term + last term /2
hence, 9+45/2=27
9×15/5=9×3
=27
9+45/2
=27