Recent questions tagged summation

0 votes
1 answer
32
5 digit numbers are possible from digits 1, 2, 3, 4, 5, 6, 7 When each digit is distinct is 7P5 . what is sum of all such numbers?
18 votes
3 answers
33
What is the sum to infinity of the series,$3+6x^{2}+9x^{4}+12x^{6}+ \dots$ given $\left | x \right |<1$$\frac{3}{(1+x^{2})}$$\frac{3}{(1+x^{2})^{2}}$$\frac{3}{(1-x^{2})^{...
4 votes
2 answers
34
Find the value of $ \Sigma ij$, where the summation is over all integers $i$ and $j$ such that $1 \leq i < j \leq 10$.
1 votes
1 answer
35
$(a) \sum_{k = 0}^{m} \left \lfloor \sqrt k \right \rfloor$$(b) \sum_{k = 0}^{m} \left \lfloor \sqrt {k^{3}} \right \rfloor$Is there any quick way to find the formula for...
1 votes
1 answer
36
$\sum_{j \in S} 1$ where S = {1, 3, 5, 7}.if we have $\sum_{j = 1}^{n} 1$ then the answer will be n. But what happens if this a set?
9 votes
1 answer
37
18 votes
2 answers
39
Use the patterns given to prove that$\sum\limits_{i=0}^{n-1} (2i+1) = n^2$(You are not permitted to employ induction)Use the result obtained in (A) to prove that $\sum\li...
17 votes
8 answers
40
Let $P =\sum \limits_ {i\;\text{odd}}^{1\le i \le 2k} i$ and $Q = \sum\limits_{i\;\text{even}}^{1 \le i \le 2k} i$, where $k$ is a positive integer. Then$P = Q - k$$P = Q...