really confused by these symbols please help

Question

sum of the series.

 

Σ^5k=1^k^2

 

A. 55

B. 56

C. 200

D. 225 

Answer 1

Hi Christine!

 

The symbols are actually quite confusing and even we tutors weren't able to understand what the problem is getting at!  I have a guess as to what you were trying to type.  It's the sum from k=1 to k=5 of k² .  If you go to www.mathim.com/chat (a math chat room), type in a username, and enter this expression, it should look like what you were probably trying to type, so try it out!  Type in:

 

$\sum_{k=1}^5 k^2$

 

If that's the case, what you're doing is, for each whole-number value of k from k=1 to k=5, you're finding the value of k², then adding up everything.  So that's:

 

1² + 2² + 3² + 4² + 5² = 1 + 4 + 9 + 16 + 25 = 55 (Answer A)

 

PS:  fun fact!  On my dad's 55th b-day, we made him a cake, and I made a pyramid using exactly 55 M&M's.  The "ground floor" had 25 M&M's, the floor on top of it had 16, the 3rd floor had 9, the 4th floor had 4, and the top floor had the last M&M on top.  I wouldn't do that anymore cuz I'm vegan now but M&M's aren't (yet), and anyway the next chance for a pyramid like that isn't going to be till my dad turns 55 + 36 = 91.