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Mathematics 17 Online
OpenStudy (anonymous):

I need help with a sequence

OpenStudy (anonymous):

10 13 16 8 If i is multiple of 4 divide it by 2 if it is not a multiple of 4 add 3 Find the 500th term The 500th term is 8 but i need a formula to show how i worked it out

OpenStudy (watchmath):

10,13,16,8,11,14,17,20,10,13,16,8 Then we can see that \(a_4=a_{12}=8\) and in general \(8=a_4=a_{4+8n}\) for any \(n\). Since \(500=4+8n\Leftrightarrow 496=8n\Leftrightarrow n=124 \) then \(a_{500}=8\).

OpenStudy (anonymous):

1. 8+3=11 2. 11+3=14 3. 14+3=17 4. 17+3=20 5. 20/2=10 6. 13 7. 16 8. 8 this will be repeating now the 4th element is 8 plus every 4+k8 element (k is an integer) 500=4+62*8 so it is 8

OpenStudy (watchmath):

Andras is right for the \(n\) :).

OpenStudy (anonymous):

The rule is if it is a multiple of 4 divide it by 2 so 8/2 =4/2=2+3=5+3=8/2=4/2=2+3=5

OpenStudy (anonymous):

that is what keeps on happening

OpenStudy (anonymous):

haha watchmath we both suck :)

OpenStudy (anonymous):

10 13 16 8 below four will be repeating than 4 2 5 8 so we can see that every 4th element is 8. 500/4=125 this proves that it is 8

OpenStudy (anonymous):

but 500 also divides by 4 so how can u be certain that it is 8

OpenStudy (anonymous):

every 4th element is an 8 (we can see that now) so if an element can be written as the the factor of 4 than it is 8. 1*4th element=8 2*4th =8 3*4th =8 and so on so the 125*4th element (500)=8

OpenStudy (anonymous):

ok thank you very much for helping me

OpenStudy (anonymous):

no prob

OpenStudy (anonymous):

What is the formula

OpenStudy (anonymous):

I dont think there is a formula here, you have to use your brain

OpenStudy (anonymous):

Are you sure because my dad says there is a formula but will not tell me

OpenStudy (anonymous):

the formula us that if the number can be written as 4k (k is an integer) than it is 8, I dont see what your dad wants.

OpenStudy (anonymous):

ok thanks i will go now and prove my dad wrong

OpenStudy (anonymous):

Good luck for that! :-)

OpenStudy (watchmath):

Well you can make a formula \(a_1=10,a_2=13,a_3=16\) \(a_{4n}=8\) for all \(n\) \(a_{4n+1}=4\) for \(n\geq 1\) \(a_{4n+2}=2\) for \(n\geq 1\) \(a_{4n+3}=5\) for \(n\geq 1\)

OpenStudy (anonymous):

can you make the formula for me pretty please

OpenStudy (watchmath):

I wrote the formula above! You need to free your mind! the formula doesn't always means that you have to write it as a single expression. The description above is count as formula too.

OpenStudy (anonymous):

ok i need to tell you something i am an 11 year old child in harrow that goes to Glebe Primary School my teacher gave me a sequnce and i had to find out the 500th term usin a simple formula do u think i can understand wat u just wrote

OpenStudy (anonymous):

at 11 you learn about sequences?? tell your teacher to relax a bit :-)

OpenStudy (anonymous):

i have to find a formula to be in this level six study group at school

OpenStudy (watchmath):

Ok, you must be smart since your teacher has a high hope for your and give you this problem. The formula that I gave above basically says that to find the nth terms of the sequence (were \(n\geq 4\) )) we do the following: When n/4 has no remainder, then the nth term is 8 when n/4 has 1 as the remainder, then the nth term is 4 when n/4 has 2 as the remainder, then the nth term is 2 when n/4 has 3 as the remainder, then then nth term is 5 For example what is the 6666th term? Lets divide 6666/4. We have 1666 with remainder 2. So the 6666th term is 2.

OpenStudy (anonymous):

ooooooooooooo i get it

OpenStudy (anonymous):

so 500/4 is 125 with no remainder so it is 8

OpenStudy (watchmath):

perfect!!

OpenStudy (anonymous):

thank u very much u are the best u should get a job as a teacher

OpenStudy (anonymous):

wat do u mean by remainder 6666/4=1666.5 so how is it 2

OpenStudy (watchmath):

\(6666=4\cdot 1666 + 2\) So the remainder is 2. You need to divide by hand to get the remainder.

OpenStudy (anonymous):

what is the hand

OpenStudy (watchmath):

By hand means not using calculator. No body teach to divide by "hand" anymore? :D

OpenStudy (anonymous):

how does 6666= 4.1666+2=

OpenStudy (anonymous):

i hav no idea where u get the remainder 2 from

OpenStudy (watchmath):

Do you know how to divide just using paper and pencil?

OpenStudy (anonymous):

yes i do

OpenStudy (watchmath):

Ok, try to divide 6666 by 4 using paper and pencil.

OpenStudy (anonymous):

ooooooo i see it now thank u very much u are the best

OpenStudy (watchmath):

good for you :D

OpenStudy (anonymous):

bye thank u so much

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