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Why in  n(n+1)/2 do you divide by 2

 Dec 1, 2019
 #1
avatar+669 
+1

you divide by 2 because the 2 is in your denominator therefore it is a fraction...... 
for example 5 divided by 2 could also be seen as 5 TIMES 1/2 :) 

hope this helps in some way. 

 Dec 1, 2019
 #2
avatar+105989 
+2

Good question guest and thanks for your answer Nivana,

I'm going to answer the same, just with slightly different words.

 

A fraction line, which is shown as / here, is exactly the same thing as a divide by sign.

 

For instance.

\(\frac{9}{2}=4\frac{1}{2}\\ 9\div 2 = 4\frac{1}{2}\\\)

 

See how the divide by sign looks like a fraction, only it has dots top and bottom instead of numbers?

Well, that is no coincidence.  

 Dec 1, 2019
 #3
avatar+1681 
+1

I've noticed in this problem there is a person icon in the corner...

 

What's that about?

 Dec 1, 2019
 #4
avatar+105989 
0

Hi Tom,

I really don't know. I don't remember seeing that symbol before.

 

 

I think it has been labelled as a high priority question. Maybe it is advertised in FaceBook or somewhere else.

It is bordered top an bottom by a heavy line in the question list.

 

 

 

GingerAle  is the one most likely to be able to answer your question.

Melody  Dec 1, 2019
edited by Melody  Dec 1, 2019
 #5
avatar+1681 
+1

Thank you!

tommarvoloriddle  Dec 1, 2019
 #13
avatar+669 
0

i think it just means moderator? :) 

oh wait! you were referring to something else LOL!

Nirvana  Dec 3, 2019
edited by Nirvana  Dec 3, 2019
 #6
avatar+8829 
+1

Maybe Guest is referring to this:

 

\(\sum\limits_{k=1}^{n}k\ =\ \frac{n(n+1)}{2}\)

 

in which case, the following might help:

 

 Dec 1, 2019
 #7
avatar+105989 
+1

mmm maybe.

Hi Hectictar!     laughcoollaugh

Melody  Dec 1, 2019
 #8
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+1

I believe hectictar is right!. I think he/she means that when you are summing up  a sequence of numbers, say from 1 to 10, why do you do this: [10 x (10+1)] / 2 = 55.

Guest Dec 1, 2019
 #9
avatar
+1

 

omg hecticar the 1+6 2+5 3+4 etc explanation  

nobody ever showed it to me that way before

it's so obvious now ... i'm so happy i'm crying

Guest Dec 1, 2019
 #10
avatar
+1

Thank you so much Hectictar. I've never thought about it like that

Guest Dec 1, 2019
 #11
avatar+8829 
+2

Glad it helped!! I learned it from one of my professors! laughsmiley

 

Also, Hi Melody!

hectictar  Dec 1, 2019
 #12
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0

what are you studying?

Guest Dec 1, 2019

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