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please help C1 sequences

i'm not sure how to tackle this? please help


Original post by kandykissesxox
i'm not sure how to tackle this? please help
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Original post by kandykissesxox


7 + 14 + ...... + 98
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Zacken
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Original post by kandykissesxox


What is the definition of a multiple of 7, would you agree that it is un=7nu_n = 7n? :smile:

What value of nn would keep un<100u_n < 100?

Sum up the series for the largest value of n for which the series does not exceed 100.
Original post by Zacken
What is the definition of a multiple of 7, would you agree that it is un=7nu_n = 7n? :smile:

What value of nn would keep un<100u_n < 100?

Sum up the series for the largest value of n for which the series does not exceed 100.

Screen Shot 2014-10-23 at 21.26.28.jpg48.2KB
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Zacken
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Original post by kandykissesxox


Correctemundo! :biggrin:
Original post by Zacken
Correctemundo! :biggrin:



thank you ! what about the second part of the question?
Sum from 0 to 99 minus your first ans. (I think, not too sure :smile: )
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Zacken
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Original post by kandykissesxox
thank you ! what about the second part of the question?


Sum of numbers to a 100 minus the sum of multiples of 7? :smile:
i.e: (1+2+3+4+5+6+...+99)−S14(1+2+3+4+5+6+...+ 99) - S_{14}

Can you evaluate the sum of 1+2+3+4+5+...+991 + 2 + 3 + 4 + 5 + ... + 99 using arithmetic series?
Original post by Zacken
Sum of numbers to a 100 minus the sum of multiples of 7? :smile:
i.e: (1+2+3+4+5+6+...+100) - S_{14}

Can you evaluate the sum of 1 + 2 + 3 + 4 + 5 + ... + 100 using arithmetic series?



i'm very sorry i'm not sure what you mean?
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Zacken
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Original post by kandykissesxox
i'm very sorry i'm not sure what you mean?


You want to take the sum of all the number that go up to 99, so 1+2+3+4+5+...+991+2+3+4+5+ ... +99 all the way to 99. That however includes number that are multiples of 7, you don't want those. So you subtract the sum of number that are multiples of 7 but are less than hundred (the previous part, you found that there) and you'll get the sum of number to 99 without including the numbers that are multiples of 7. :smile:

What is the sum of 1+2+3+4+5+...+991+2+3+4+5+...+99
Original post by Zacken
You want to take the sum of all the number that go up to 99, so 1+2+3+4+5+...+991+2+3+4+5+ ... +99 all the way to 99. That however includes number that are multiples of 7, you don't want those. So you subtract the sum of number that are multiples of 7 but are less than hundred (the previous part, you found that there) and you'll get the sum of number to 99 without including the numbers that are multiples of 7. :smile:

What is the sum of 1+2+3+4+5+...+991+2+3+4+5+...+99


so do i incorporate 735 or not?
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Zacken
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Original post by kandykissesxox
so do i incorporate 735 or not?


You subtract 735 from the sum of 1+2+3+4+5+...+99. :smile:
Original post by Zacken
You subtract 735 from the sum of 1+2+3+4+5+...+99. :smile:


i got an answer of 4215? :smile:
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Zacken
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Original post by kandykissesxox
i got an answer of 4215? :smile:


Correct! :biggrin:
Original post by zacken
correct! :d


thank you so much!!!! Xxxx

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