A community for students.

Here's the question you clicked on:

55 members online
  • 0 replying
  • 0 viewing

anonymous

  • one year ago

help please! Evaluate the summation of 20 times 0.5 to the n minus 1 power, from n equals 3 to 12.. 9.99 19.95 29.98 39.96

  • This Question is Closed
  1. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    \[\sum_{n=3}^{12} 20 \times 0.5^{n-1}\] This is it, right?

  2. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yes

  3. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    @larryboxaplenty

  4. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    I can't help you right now, sorry, g2g for a sec someone else can help. I know the answer for forget the shortcut

  5. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    can someone please help me

  6. Jhannybean
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    \[\large 20 \cdot \left(0.5^{n-1}\right)\] start with plugging in \(n=3\) and work your way up to \(n=12\) by adding all the values.

  7. Jhannybean
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 1

    \[\large 20\cdot (0.5^{3-1} + 0.5^{4-1}+0.5^{5-1}+...+0.5^{12-1})\]

  8. welshfella
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    or you can use the formula for the sum of a geometric series Sn = a . (1 - r^n) ------ 1 - r

  9. welshfella
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    here a = 20*0.5^2 , n = 11 and r = 0.5

  10. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    so would i get 9.99 as the answer

  11. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    @welshfella

  12. welshfella
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yes

  13. anonymous
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    thank you

  14. welshfella
    • one year ago
    Best Response
    You've already chosen the best response.
    Medals 0

    yw

  15. Not the answer you are looking for?
    Search for more explanations.

    • Attachments:

Ask your own question

Sign Up
Find more explanations on OpenStudy
Privacy Policy

Your question is ready. Sign up for free to start getting answers.

spraguer (Moderator)
5 → View Detailed Profile

is replying to Can someone tell me what button the professor is hitting...

23

  • Teamwork 19 Teammate
  • Problem Solving 19 Hero
  • You have blocked this person.
  • ✔ You're a fan Checking fan status...

Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.

This is the testimonial you wrote.
You haven't written a testimonial for Owlfred.