Madhya Pradesh Police Exam Model Paper 8

Given:
8 multiples of 13
Formula Used:
Arithmetic mean = Sum of terms/Number of terms
Sum of an arithmetic progression = (number of terms/2) × ( first term + last term)
nth term of an Arithmetic progression = first term + (n – 1) × common difference
Common difference = second term – first term
Calculation:
multiple of 13 ⇒ common difference = 13
First term = 13
8th term $=13+\left(8\mathit{–}1\right)13$
⇒ 8th term $=13+91$

⇒ 8th term $=104$
Sum of arithmetic progression $=\left(8/2\right)\times \left(13+104\right)$
$\Rightarrow 4\times 117$
$\Rightarrow 468$
Arithmetic mean $=468/8$
$\Rightarrow 58.5$
∴ Arithmetic mean of first 8 multiples of 13 is 58.5