Question

A set of ‘n’ numbers has the sum ‘s’. 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 + 20 n 

(B) 5s + 80n 

(C) s 

(D) 5s + 4n

Answer 1

Correct Option:- (B) 5s + 80n

Explanation :-

Let numbers be a₁ , a₂ , a₃ , a₄ ......,a_n 

 S = a₁ + a₂ + ..... + a _n 

If each number is increased by 20, multiplies by 5 & then decresed by 20 then

a' i = (ai + 20)5 – 20 = 5a'_i + 80 

i = 1, 2, 3,.....,n 

so S' = a' 1 + a'2 + a'3 + ......+a'_n 

= 5(a₁ + a₂ + a₃ +.....+ a_n ) + n.80 = 5S + 80 n