Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

Pages: **1**

**Monox D. I-Fly****Member**- From: Indonesia
- Registered: 2015-12-02
- Posts: 2,000

Determine the value of

I know that it means , but how do I answer? It's from a student worksheet for 7th graders, so they haven't learnt about sequence and series yet. Granted, the book also says that the question was from a middle school-level math contest.

Actually I never watch Star Wars and not interested in it anyway, but I choose a Yoda card as my avatar in honor of our great friend bobbym who has passed away.

May his adventurous soul rest in peace at heaven.

Offline

**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,903

hi

The denominators are 'triangle numbers' and there's a formula for those.

n(n+1)/2

Then you can use partial fractions to split each term into two fractions, one positive and one negative.

Most terms then cancel out.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Sometimes I deliberately make mistakes, just to test you! …………….Bob Bundy

Offline

**Monox D. I-Fly****Member**- From: Indonesia
- Registered: 2015-12-02
- Posts: 2,000

That confirms me that it's definitely not supposed to be for a 7th grader.

Actually I never watch Star Wars and not interested in it anyway, but I choose a Yoda card as my avatar in honor of our great friend bobbym who has passed away.

May his adventurous soul rest in peace at heaven.

Offline

**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,903

Actually it is possible to do the steps just with fractions:

The second term in each bracket cancels with the first term in the next.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Sometimes I deliberately make mistakes, just to test you! …………….Bob Bundy

Offline

**Monox D. I-Fly****Member**- From: Indonesia
- Registered: 2015-12-02
- Posts: 2,000

bob bundy wrote:

Actually it is possible to do the steps just with fractions:

The second term in each bracket cancels with the first term in the next.

Bob

darn, never thought of that! Now, THIS is beautiful! Thanks, bob bundy!

Actually I never watch Star Wars and not interested in it anyway, but I choose a Yoda card as my avatar in honor of our great friend bobbym who has passed away.

May his adventurous soul rest in peace at heaven.

Offline

Pages: **1**