Question

The maximum sum of the series is.

• A. 310
• B. 300
• C. 320
• D. None of these

Answer 1

Answer: (A)

310

Answer 2

$n ^ { t h }$ term of the series is $20 + ( n - 1 ) \left( - \frac { 2 } { 3 } \right)$.

For sum to be maximum, $n ^ { t h }$ term $\geq 0$

$\Rightarrow$ $20 + ( n - 1 ) \left( - \frac { 2 } { 3 } \right) \geq 0$ $\Rightarrow$ $n \leq 31$

Thus the sum of 31 terms is maximum and is equal to

$\frac { 31 } { 2 } \left[ 40 + 30 \times \left( - \frac { 2 } { 3 } \right) \right] = 310$.