Question

A set numbers has the sum ${}^{\prime }{S}^{\prime }$. Each number of the set is increased by $20$, then multiplied by $5$, and then decreased by $20$. The sum of the numbers in the new set thus obtained is :

• A. $S+20n$
• B. $5S+80n$
• C. $5S+4n$
• D. $5S$

Answer 1

Answer: (B)

$5S+80n$

Let there be n numbers
$x_1,x_2,.......x_n$.
So $x_1+x_2+.......+x_n=S$
According to equation new sum is
$\left\{5\right(x_1+20)-20\}+\left\{5\right(x_2+20)-20\}+.....+\left\{5\right(x_n+20)-20\}$
$4=5(x_1+x_2+......+x_n)+80+80+......80$
$=5S+80n$