AP ICET 2016 Paper

Given observations : 7, 10, 13, 16, ......., 121
The above observation are in A.P and σ is their S.D.
    $7,$ $10,$ $13,$ $16,$......$121$
$\left(\times 7+1\right)$$\downarrow$ $\downarrow$ $\downarrow$ $\downarrow$  $\downarrow$
    $50,$$71,$ $92,$ $113.$.....$848$
The second set of observations is obtained by multiplying observations of the first set by 7 and adding 1 to the product.
∴Required S.D of (50, 71, 92, 113, ........, 848) = 7σ