Question

- Students in class are exchanging pencils.
1 student = 0 exchanges
2 students = 2 exchanges
3 students = 6 exchanges
4 students = 12 exchanges

how many exhcanges for 7 sutudents?

*I know the answer to be: 42 exchanges... but how to get it??? I knwo there is a formula, but I dont knwo how is it and how to use it..* help

Answer 1

1 * 0 = 0
2 * 1 = 2
3 * 2 = 6
4 * 3 = 12
5 * 4 = 20
6 * 5 = 30
7 * 6 = 42

Answer 2

yes, thats how i got it... but i know there is a formula... something like an=2n-1+(n-1) or something like that... (not sure if its that one.... and i know how to use that formula... nor i dont kknow what the formula menas.. :/

Answer 3

Okay.
Math in the morning ^_^.
There's a pattern.
1 student = 0 exchanges
2 students = 2 exchanges
3 students = 6 exchanges
4 students = 12 exchanges
S students = X exchanges
S students = X exchanges
7 students = 42 exchanges

S = Students
X = Exchanges
The pattern is how many number of students there is minus one from it then times it by that number.
So:
S - 1 = Number to multiple by let's call it (N).
S * N = X
Let's test it:
First say there are 10 students.
10 - 1 = 9
10 * 9 = 90 Exchanges.

Get it?

Answer 4

but why S-1???

Answer 5

Nobody knows...

Answer 6

Because. The pattern shows that the number multiplied by the students is always one less than it.

Answer 7

still dont get it.. (sorry for the persistance..) i wanna learn math like for real..

Answer 8

So the formula is:
(S - 1) = N
S * N = X
S = Students
X = Exchanges
N = Number to multiple on "S".

Answer 9

Say there is:
120 students = ? exchanges
Now use the formula:
(S - 1) = N
S = 120
So (120 - 1) = 119
N = 119
Now for step two:
S * N = X
We know what S and N are now so plug in the values:
120 * 119 = 14,280
14,280 = X

And again:
S = Students
X = Exchanges
N = Number to multiple on "S".

Answer 10

yeah.. i get that... i just didnt know why N = S-1 ... but its ok tho... thanks man! :)

Answer 11

u are a really good helper :- )

Answer 12

So the formula is:
(S - 1) = N <-- S is for Students (Given) N is for the Number to multiple on "S". IN the pattern to get N. In this case we minus by "1".
Then leading us to:
S * N = X
S = Students
X = Exchanges
N = Number to multiple on "S".

And no problem ^_^.

Answer 13

I am waiting to help like Opcode. :-(

Answer 14

Help me with what O.o?
My stuff is just memorizing things like postulates and theorems.
Memory with numbers = Head Ache. (For me at lest).

Answer 15

ahah...