Aptitude | Progressions | Question 5

Find sum of series: 2, 2.5, 3, 3. 5, 4, 4. 5……….11
(A) 120
(B) 123.5
(C) 126.5
(D) 118.5


Answer: (B)

Explanation: sum of AP = (n/2)[2a+(n-1)d]
n=19, a=2, d=1/2
S = (19/2)[2*2+(19-1)1/2]
=(19/2)[4+9]
=9.5*13 = 123.5


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