# Thread: [GCSE-O] Number Sequence And Standard Deviation

1. ## [GCSE-O] Number Sequence And Standard Deviation

Hi all. I am doing revision for Elementary and Additional Mathematics and need help with the following question for my elementary mathematics GCSE O Level.
Thank you.

I hope someone is able to help me with the following questions. Thank you very much

1) Find the next two value of the sequence

7/8 , 2/3 , 1/2 , 4/11 , 1/4

I can't figure out any formula for this.
I tried using the arithmetic and geometric sequences and series, but I still can't find it.

2) A data has the following value, a, b, c, 4 and 8. The mean for a, b, and c, is 8

the standard deviation for a b and c is sqrt(7)

find the standard deviation for the 5 values.

I did up till (a-8)2 + (b-8)2 + (c-8)2 = 21

I found the mean for the 5 values is 7.2.

Thank you for reading and the help!

2. ## Re: [GCSE-O] Number Sequence And Standard Deviation

Hello, mynameiscosine!

$\text{(1) Find the next two values of the sequence: }\:\frac{7}{8},\;\frac{2}{3},\;\frac{1}{2},\;\frac {4}{11},\;\frac{1}{4}\,\hdots$

This requires a "trick" that you haven't thought of . . .

Re-write the fractions: . $\frac{7}{8},\;\frac{6}{9},\;\frac{5}{10},\;\frac{4 }{11},\;\frac{3}{12},\;\hdots$

Got it?

3. ## Re: [GCSE-O] Number Sequence And Standard Deviation

@Soroban

Ohhh!

I should have seen this pattern. You made it so easy! lol
The next two number should be

2/13, 1/14

Am I right?

Thank you very much!

How about the second question for standard deviation?
Thanks again!