The maximum sum of the series 20 + 19frac{1}{ | vedclass

Name: Exam Paper Generator | JEE NEET Paper Generator | Vedclass
Brand: Vedclass
Rating: 5 (35 reviews)

Question

(A) The given series is an arithmetic progression with the first term $a = 20$ and common difference $d = 19\frac{1}{3} - 20 = -\frac{2}{3}$.The $n^{t

Vedclass · Accepted Answer

$310$

Vedclass · Answer

(A) The given series is an arithmetic progression with the first term $a = 20$ and common difference $d = 19\frac{1}{3} - 20 = -\frac{2}{3}$.The $n^{th}$ term of the series is given by $a_n = a + (n - 1)d = 20 + (n - 1)\left( -\frac{2}{3} ight)$.For the sum to be maximum,we consider all positive terms of the series,i.e.,$a_n \ge 0$.$20 - \frac{2}{3}(n - 1) \ge 0$$20 \ge \frac{2}{3}(n - 1)$$30 \ge n - 1$$n \le 31$.Thus,the sum of the first $31$ terms is the maximum sum.$S_{31} = \frac{31}{2} [2a + (31 - 1)d] = \frac{31}{2} [2(20) + 30(-\frac{2}{3})]$$S_{31} = \frac{31}{2} [40 - 20] = \frac{31}{2} 	imes 20 = 310$.

The maximum sum of the series $20 + 19\frac{1}{3} + 18\frac{2}{3} + \dots$ is

Similar Questions

For $n \in N$,what is the value of $1+4+7+\cdots+(3n-2)$?

If the sum of $n$ terms of an arithmetic progression is given by $Pn + Qn^2$,where $P$ and $Q$ are constants,what is the common difference?

If the roots $\alpha, \beta, \gamma$ of the equation $x^3-6x^2+px+10=0$ are in arithmetic progression,then $\alpha^3+\beta^3+\gamma^3=$

If $2x, x + 8$ and $3x + 1$ are in an arithmetic progression,then $x = \dots$

If $2x, x + 8, 3x + 1$ are in $A.P.$,then the value of $x$ will be

Vedclass Test Series

Exam Paper Generator

Online Exam Module