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

You are not logged in.

- Topics: Active | Unanswered

**jacks****Member**- Registered: 2012-11-21
- Posts: 80

In a Diagram shown in figure, Not that the Grid path from **F** to **G** is missing.

So path from **A** to **B** can not pass from **F** and **G**.

How many path are there from **A** to **B**

assume all path only have steps going up or to the right.

*Last edited by jacks (2013-09-29 05:30:44)*

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,455

Where is D and E?

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

Offline

**jacks****Member**- Registered: 2012-11-21
- Posts: 80

Sorry Bobbym , actually it is **A** and **B**

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,455

Hi;

I am getting 38 ways.

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

Offline

**jacks****Member**- Registered: 2012-11-21
- Posts: 80

Would you like to explain it to me, Thanks

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,455

For ones that have missing intersections and are small the vertex counting method will work fine.

The drawing shows the number of paths to each node.

Each node is the sum of the two nodes underneath and to left of it.

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

Offline

**jacks****Member**- Registered: 2012-11-21
- Posts: 80

Thanks Bobbym Got it.

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,455

There is an analytical answer for these type but the counting method is easier to understand.

**In mathematics, you don't understand things. You just get used to them.**

Offline

**jacks****Member**- Registered: 2012-11-21
- Posts: 80

Would you like to explain me analytical answer.

I also tried for that method but could not get it.

(But I like yours Counting method.)

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,455

Hi;

By combinatorics:

**In mathematics, you don't understand things. You just get used to them.**

Offline

**jacks****Member**- Registered: 2012-11-21
- Posts: 80

Thanks Bobbym would you like to explain me to it.

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,455

It is just adding up all the paths in the lattice around the missing intersection.

**In mathematics, you don't understand things. You just get used to them.**

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,657

Hi

is also a way.Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

Offline

**jacks****Member**- Registered: 2012-11-21
- Posts: 80

To anonimnystefy I have understand

(Which is Total no. of path from **A** to **B**, If There is a connectivity between F to G)

but Did not understand

Would you explain it to me.

Thanks

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,657

It's the number of paths from A to F times the number of paths from G to B.

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

Offline

**jacks****Member**- Registered: 2012-11-21
- Posts: 80

To Admin (Bobbym) i did not understand it

It is just adding up all the paths in the lattice around the missing intersection.

Thanks

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,657

I think I know which points he took, but I cannot be sure.

I think he used (2,3), (3,0) and (3,1), A being (0,0) and B being (5,4).

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,455

Hi;

Look at my drawing in post #6.

I picked (2,3), (3,1) and (4,0) and calculated the paths from there.

**In mathematics, you don't understand things. You just get used to them.**

Offline

**jacks****Member**- Registered: 2012-11-21
- Posts: 80

It's the number of paths from A to F times the number of paths from G to B.

To anonimnystefy I did not understand it

why we minus it.

please explain it to me

Thanks

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,657

anonimnystefy wrote:

It's the number of paths from A to F times the number of paths from G to B.

This is the reason. These are all the paths that become unavailable when we remove the line.

Hi bobbym

Yes, I meant (4,0).

*Last edited by anonimnystefy (2013-09-30 07:59:54)*

Here lies the reader who will never open this book. He is forever dead.

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,455

Hi;

I did not see your post 17, I was answering his question.

**In mathematics, you don't understand things. You just get used to them.**

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,657

Even better then.

I guess the question is fully answered now. Three ways is enough.

I just want to try to do one more thing.

*Last edited by anonimnystefy (2013-09-30 08:04:30)*

Here lies the reader who will never open this book. He is forever dead.

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,455

There is another more general way. That maybe can answer for many missing intersections.

**In mathematics, you don't understand things. You just get used to them.**

Offline

**jacks****Member**- Registered: 2012-11-21
- Posts: 80

Thanks Admin and anonimnystefy got it

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 90,455

Hi;

You are wlecome.

**In mathematics, you don't understand things. You just get used to them.**

Offline