1 + frac{1^3 + 2^3}{1 + 2} + frac{1^3 + 2^3 + | vedclass

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

Question

(A) The $n^{th}$ term of the series is $T_n = \frac{\sum_{k=1}^n k^3}{\sum_{k=1}^n k}$.Using the formulas $\sum_{k=1}^n k^3 = \left[ \frac{n(n+1)}{2}

Vedclass · Accepted Answer

$620$

Vedclass · Answer

(A) The $n^{th}$ term of the series is $T_n = \frac{\sum_{k=1}^n k^3}{\sum_{k=1}^n k}$.Using the formulas $\sum_{k=1}^n k^3 = \left[ \frac{n(n+1)}{2} \right]^2$ and $\sum_{k=1}^n k = \frac{n(n+1)}{2}$,we get:$T_n = \frac{[n(n+1)/2]^2}{n(n+1)/2} = \frac{n(n+1)}{2}$.The total sum is $S = \sum_{n=1}^{15} T_n - \frac{1}{2} \sum_{n=1}^{15} n$.$S = \sum_{n=1}^{15} \frac{n(n+1)}{2} - \frac{1}{2} \cdot \frac{15 \cdot 16}{2}$.$S = \frac{1}{2} \left[ \sum_{n=1}^{15} n^2 + \sum_{n=1}^{15} n \right] - 60$.$S = \frac{1}{2} \left[ \frac{15(16)(31)}{6} + \frac{15(16)}{2} \right] - 60$.$S = \frac{1}{2} [1240 + 120] - 60 = \frac{1360}{2} - 60 = 680 - 60 = 620$.

$1 + \frac{1^3 + 2^3}{1 + 2} + \frac{1^3 + 2^3 + 3^3}{1 + 2 + 3} + \dots + \frac{1^3 + 2^3 + 3^3 + \dots + 15^3}{1 + 2 + 3 + \dots + 15} - \frac{1}{2}(1 + 2 + 3 + \dots + 15)$ is equal to

Similar Questions

The sum of the following series $1 + 6 + \frac{9(1^2 + 2^2 + 3^2)}{7} + \frac{12(1^2 + 2^2 + 3^2 + 4^2)}{9} + \frac{15(1^2 + 2^2 + ... + 5^2)}{11} + ...$ up to $15$ terms is:

$\frac{1}{1 \cdot 2} + \frac{1}{2 \cdot 3} + \frac{1}{3 \cdot 4} + \dots + \frac{1}{n(n + 1)}$ equals

Let $f(n) = [\frac{1}{3} + \frac{3n}{100}]n$,where $[x]$ denotes the greatest integer less than or equal to $x$. Then $\sum_{n=1}^{56} f(n)$ is equal to

The mean of the series $a, a + nd, a + 2nd$ is

If $a, b, c, d$ are in $H.P.$,then

Vedclass Test Series

Exam Paper Generator

Online Exam Module