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Exams...maths - WTH by M73A on 04-21-2005 at 10:40 AM

right, this was the first question on my maths exam today:|.....i even wrote it on my hand to try it later but i still dont get it...

well heres the question:

A - what are the next to numbers in this sequence:
3, 12, 27, 48, 75, __, __.

B - show the nth number in terms of n



-so gonna get made to look absolutely stupid but i wondered if anyone here would get an answer *-)

RE: Exams...maths - WTH by x2zen on 04-21-2005 at 10:51 AM

3, 12, 27, 48, 75, 108, 147

RE: Exams...maths - WTH by Dempsey on 04-21-2005 at 10:52 AM

The next two numbers would be 108 and 147

not sure about calculating the nth term tho, ill have it in a sec

RE: Exams...maths - WTH by M73A on 04-21-2005 at 10:52 AM

quote:
Originally posted by A. Madsen
3, 12, 27, 48, 75, 108, 147

ok, how the hell you get that:S plus thats only part A :tongue:
RE: Exams...maths - WTH by x2zen on 04-21-2005 at 10:55 AM

quote:
Originally posted by may73alliance
quote:
Originally posted by A. Madsen
3, 12, 27, 48, 75, 108, 147

ok, how the hell you get that:S plus thats only part A
The difference between 2 numbers is incresing with 6 every number.
The difference between 3 and 12 is 9
The difference between 12 and 27 is 15

The difference between 9 and 15 is 6
:)
RE: Exams...maths - WTH by Dempsey on 04-21-2005 at 10:57 AM

if you look at the difference between them

12 - 3  = 9

        15 - 9 = 6

27 - 12 = 15

        21 - 15 = 6

48 - 27 = 21

        27 - 21 = 6

75 - 48 = 27


I can't rememebr the way to calculate the nth term, its been 3 years since i was doing this kinda stuff at school

RE: Exams...maths - WTH by M73A on 04-21-2005 at 10:57 AM

quote:
Originally posted by A. Madsen
quote:
Originally posted by may73alliance
quote:
Originally posted by A. Madsen
3, 12, 27, 48, 75, 108, 147

ok, how the hell you get that:S plus thats only part A
The difference between 2 numbers is incresing with 6 every number.
The difference between 3 and 12 is 9
The difference between 12 and 27 is 15

The difference between 9 and 15 is 6
:)
ahhh man:| missed easy marks on my exams then, lol.... :dodgy: seems simple now i know how it works.... thanks (Y)


still.....whats it in terms of n then:P
RE: Exams...maths - WTH by Dempsey on 04-21-2005 at 11:01 AM

well its n - (n-1)=6  but i cant rememebr how to make it so its n= ??

RE: Exams...maths - WTH by .Roy on 04-21-2005 at 11:03 AM

n- (n-1) = 6
n -n +1 = 6
0=5?

It doesnt work out...

RE: Exams...maths - WTH by Daryl on 04-21-2005 at 11:08 AM

Hi may73alliance

The formula to calculate term n is (n^2) * 3.

Hope ur gonna have a good grade on this ;)

RE: Exams...maths - WTH by linx05 on 04-21-2005 at 12:09 PM

Hehe programmers are usually good with math...

RE: Exams...maths - WTH by M73A on 04-21-2005 at 12:27 PM

quote:
Originally posted by Daryl
Hi may73alliance

The formula to calculate term n is (n^2) * 3.

Hope ur gonna have a good grade on this ;)

lol so do i :tongue: don't look like it though, lol owel :cheesy:
RE: Exams...maths - WTH by haydos on 04-21-2005 at 12:28 PM

Well Daryl's answer is right but I got the B section differently (although a little more confusing.)

My result was:
           n= [(n-1)-(n-2)+6] + (n-1)

eg.
In this example I will use 108 as n, therefore (n-1) = 75 and (n-2) is 48
We want to calculate n so i will write the equation as
             n= (75-48+6)+75
therefore n=108

I know my method takes more effort to reach the same answer that Daryl got but depending on the wording of the question, you may not be allowed to put the nth term on each side as is done in Daryls...
Hope this helps


quote:
Originally posted by Dempsy
well its n - (n-1)=6
It's actually (n-1)-(n-2)=6;)
RE: Exams...maths - WTH by M73A on 04-21-2005 at 12:35 PM

quote:
Originally posted by inc_haydn
Hope this helps

its helped me undertsand it but shame cant use it on the bloody exam:|. lol, i think that is kinda hard for the 1st question though:|:|:|:|:|:|:|
RE: RE: Exams...maths - WTH by Dempsey on 04-21-2005 at 02:06 PM

quote:
Originally posted by inc_haydn
quote:
Originally posted by Dempsy
well its n - (n-1)=6
It's actually (n-1)-(n-2)=6;)
well i was close lol
RE: Exams...maths - WTH by ddunk on 04-21-2005 at 02:14 PM

quote:
Originally posted by inc_haydn
It's actually (n-1)-(n-2)=6

that formula doesn't work either, remember it's a sequence, not a normal algebratic expression, so n doesn't equal any random number, n equals the nth number. so...

0, 1  , 2  , 3  , 4  , 5  , 6
3, 12, 27, 48, 75, __, __.

for 3, n=0, for 75, n=4 and so on.

I can't solve it right now, cause i've got school, but have fun :p
RE: Exams...maths - WTH by John Anderton on 04-21-2005 at 02:20 PM

See the sequence is this ....
3, 12, 27, 48, 75, 108, 147

(1^2)*3 = 1 * 3 = 3
(2^2)*3 = 4 * 3 = 12
(3^2)*3 = 9 * 3 = 27
(4^2)*3 = 16 * 3 = 48
(5^2)*3 = 25 * 3 = 75
(6^2)*3 = 36 * 3 = 108
(7^2)*3 = 49 * 3 = 147

Nth term is (n^2)*3
:cheesy:
ie ... n square into 3 ;) (for ppl who may not understand the symbols but im sure most ppl do)

RE: Exams...maths - WTH by ddunk on 04-21-2005 at 02:26 PM

quote:
Originally posted by John Anderton
See the sequence is this ....
3, 12, 27, 48, 75, 108, 147

(1^2)*3 = 1 * 3 = 3
(2^2)*3 = 4 * 3 = 12
(3^2)*3 = 9 * 3 = 27
(4^2)*3 = 16 * 3 = 48
(5^2)*3 = 25 * 3 = 75
(6^2)*3 = 36 * 3 = 108
(7^2)*3 = 49 * 3 = 147

Nth term is (n^2)*3
:cheesy:
ie ... n square into 3 ;) (for ppl who may not understand the symbols but im sure most ppl do)

Sequences start with 0 though, you're close, but the 0 need to equal 3
RE: Exams...maths - WTH by M73A on 04-21-2005 at 02:26 PM

lol, this is beyond a joke. now i've looked at it how JA has set it out its soooo bloody simple......is there a emoticon with a dunce hat? *place one here*

EDIT:S ok now Ddunk sayin JA's is wrong, ohhh sooooo confused :S!

RE: Exams...maths - WTH by haydos on 04-21-2005 at 02:56 PM

hehe just use the green formula I put and ignore what i wrote correcting Dempsy...

          n= [(n-1)-(n-2)+6] + (n-1)

And this does work. As for DDunk saying 0 is the first number that also works with this equation.

If I used the 1st figure (3) and substitute all of the blue numbers below into my equation, this is what results:

n=3
(n-1)=0
(n-2)=3 (I got this answer because it must be the opposite of the 3 ie the system is a quadratic)

      therefore n= (0-3+6)+0
                        =3

**********
 
Actual value of n          -2         -1         0           1           2        3             4              5

Actual number value      12         3          0            3         12       27          48           75
                                 
No.s used in example   (n-3)     (n-2)    (n-1)        (n)        (n+1)      (n+2)      (n+3)     (n+4)

RE: Exams...maths - WTH by Smethead on 04-21-2005 at 03:25 PM

quote:
Originally posted by Ddunk
quote:
Originally posted by John Anderton
See the sequence is this ....
3, 12, 27, 48, 75, 108, 147

(1^2)*3 = 1 * 3 = 3
(2^2)*3 = 4 * 3 = 12
(3^2)*3 = 9 * 3 = 27
(4^2)*3 = 16 * 3 = 48
(5^2)*3 = 25 * 3 = 75
(6^2)*3 = 36 * 3 = 108
(7^2)*3 = 49 * 3 = 147

Nth term is (n^2)*3
:cheesy:
ie ... n square into 3 ;) (for ppl who may not understand the symbols but im sure most ppl do)

Sequences start with 0 though, you're close, but the 0 need to equal 3
((n+1)^2)*3 :d
RE: Exams...maths - WTH by haydos on 04-21-2005 at 03:34 PM

quote:
Originally posted by Smethead
quote:
Originally posted by Ddunk
Sequences start with 0 though, you're close, but the 0 need to equal 3
((n+1)^2)*3 :d

This would only work when n=0, otherwise it is incorrect
:)
RE: RE: Exams...maths - WTH by gif83 on 04-21-2005 at 05:03 PM

quote:
Originally posted by inc_haydn
quote:
Originally posted by Smethead
quote:
Originally posted by Ddunk
Sequences start with 0 though, you're close, but the 0 need to equal 3
((n+1)^2)*3 :d

This would only work when n=0, otherwise it is incorrect
:)

I don't know what you are saying... have you even tried it?

quote:
Originally posted by Ddunk
Sequences start with 0 though, you're close, but the 0 need to equal 3

erm not really... not many people talk about the 0th term. sequences tend to start from the 1st term.
RE: RE: RE: Exams...maths - WTH by haydos on 04-21-2005 at 05:09 PM

quote:
Originally posted by gif83
quote:
Originally posted by inc_haydn
quote:
Originally posted by Smethead
quote:
Originally posted by Ddunk
Sequences start with 0 though, you're close, but the 0 need to equal 3
((n+1)^2)*3 :d

This would only work when n=0, otherwise it is incorrect
:)

I don't know what you are saying... have you even tried it?
Yes i tried it for all of the other options showed there, for example; inserting n=2 gives ((3^2)x3) which is equal to 27... when n=2 the number is 12......

quote:
Originally posted by gif83
erm not really... not many people talk about the 0th term. sequences tend to start from the 1st term.
Even though "not many people talk about it" as you say, it doesnt mean its not there. What if there was a part C to the question asking;
If n=0 what is the equivalent number in the sequence?
RE: Exams...maths - WTH by gif83 on 04-21-2005 at 05:22 PM

quote:
Originally posted by inc_haydn
Even though "not many people talk about it" as you say, it doesnt mean its not there. What if there was a part C to the question asking;
If n=0 what is the equivalent number in the sequence?

thanks for clarifying... :) i thought that you were actually talking about the same thing as Ddunk.

so (n^2)*3 still works
RE: Exams...maths - WTH by haydos on 04-21-2005 at 05:30 PM

quote:
Originally posted by gif83
quote:
Originally posted by inc_haydn
Even though "not many people talk about it" as you say, it doesnt mean its not there. What if there was a part C to the question asking;
If n=0 what is the equivalent number in the sequence?

thanks for clarifying... :)
No problem

quote:
Originally posted by toddler
tbh lets face it......u will have failed :P

that first question was easy |-)
Yeah if your having that much trouble with the first question you better start collecting some teacher bribes:P (btw it wasnt thaaat easy)
RE: Exams...maths - WTH by toddy on 04-21-2005 at 05:33 PM

quote:
Originally posted by inc_haydn
it wasnt thaaat easy

it was |-)

then again i got a B in my A-level futher maths and i didn't even go to lessons half the time :P

maths is just easy

(got kicked out in the end :cry: :))
RE: Exams...maths - WTH by M73A on 04-21-2005 at 07:12 PM

quote:
Originally posted by toddler
quote:
Originally posted by inc_haydn
it wasnt thaaat easy

it was |-)

then again i got a B in my A-level futher maths and i didn't even go to lessons half the time :P

maths is just easy

(got kicked out in the end :cry: :))
1 - maths aint easy:P lol
2 - why you get kicked out? lol =
[Image: go_you.gif]
RE: Exams...maths - WTH by TylerG on 04-21-2005 at 09:58 PM

Since when did sequences start with 0?

RE: Exams...maths - WTH by toddy on 04-21-2005 at 10:11 PM

quote:
Originally posted by may73alliance
2 - why you get kicked out? lol =
quote:
Originally posted by toddler
and i didn't even go to lessons half the time
RE: Exams...maths - WTH by ddunk on 04-21-2005 at 10:14 PM

quote:
Originally posted by TylerG

Since when did sequences start with 0?

After talking with Segosa... apparently not always. Only way I've ever seen them written is starting with 0, even on the PSAT/SAT (US Nationalized test). Sorry about my American dodginess :<