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# Edexcel C1 arithmetic series question 5 January 2014 IAL paper watch

1. Hi,

How would you do parts (b) and (c) for this question?
Please could you also show the steps to how you got the answer as well?

Thank you!
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2. (Original post by Shanahey)
Hi,

How would you do parts (b) and (c) for this question?
Please could you also show the steps to how you got the answer as well?

Thank you!
(b) and (c) rely on (a). What did you get for those values?

It helps to think about what went on from u2 to u3 to u4, and what u5 will be.
3. (Original post by SeanFM)
(b) and (c) rely on (a). What did you get for those values?

It helps to think about what went on from u2 to u3 to u4, and what u5 will be.
Hi,
I got U2 as 2/3, U3 as -4 and u4 as 3
4. (Original post by Shanahey)
Hi,
I got U2 as 2/3, U3 as -4 and u4 as 3
Brilliant

Without further calculation, can you see what u5 would be? (You can calculate it if you want but hopefully you spot something else).
5. (Original post by SeanFM)
Brilliant

Without further calculation, can you see what u5 would be? (You can calculate it if you want but hopefully you spot something else).
U5 would be 2/3?
6. (Original post by Shanahey)
U5 would be 2/3?
Bingo. Can you see the pattern?
7. (Original post by SeanFM)
Bingo. Can you see the pattern?
Yeah I can see the pattern, but how would you find U61 straight away?
8. (Original post by Shanahey)
Yeah I can see the pattern, but how would you find U61 straight away?
Well, the terms seem to appear in sets (which you'll have worked out as sets of 3 - a,b,c).

So U1 = a, U2 = b, U3 = c (for the first 3 numbers), U4 = a .... (for the numbers 4-6)... what will U61 be?
9. (Original post by SeanFM)
Well, the terms seem to appear in sets (which you'll have worked out as sets of 3 - a,b,c).

So U1 = a, U2 = b, U3 = c (for the first 3 numbers), U4 = a .... (for the numbers 4-6)... what will U61 be?
Thank you! How would you do part (c)?
10. (Original post by Shanahey)
Thank you! How would you do part (c)?
The clue is that it's the sum of the *99* terms. Now think about your set of .... and you should be able to find the sum.

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