Hello,(adsbygoogle = window.adsbygoogle || []).push({});

I'm having some issues solving some apparently 'basic' summation problems where they give you a couple summations and you derive the missing summation.

I would appreciate any help not only solving this particular question but actually understanding the situation.

Thanks!

1. The problem statement, all variables and given/known data

Suppose:

113

[tex]\Sigma[/tex] a_{k}= 641

k=9

and

507

[tex]\Sigma[/tex] a_{k}= 2091

k=70

and

113

[tex]\Sigma[/tex] a_{k}= 130

k=70

Then:

507

[tex]\Sigma[/tex] a_{k}= ?

k=114

2. Relevant equations

I think everything relevant is provided above.

3. The attempt at a solution

I have absolutely no idea how to start. I've googled summation problems and read quite a bit more than what is in my text. I keep finding information on what I can already do; problems like:

10

[tex]\Sigma[/tex] a-20 = ?

k=1

Where a is a constant instead of having the 'k' subscript so you can take (10-(1-1)) * (a-20).

Although, for some reason sticking the subscript onto a throws me off completely. Any suggestions are welcome.

Thank you for your time!

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Some basic summation problems

**Physics Forums | Science Articles, Homework Help, Discussion**