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    Ok, having trouble with a different question if anyone can help.

    Find the sum of the integers, between 1 and 300 inclusive, not divisable by 3.

    Where do I start. Do i need an equation for a number not divisable by 3?

    Thanks

    Louise
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    You need an equation for the sum of the numbers divisable by 3. You can then find out the sum of all the integers between 1 and 300 and subtract the some of the numbers divisable by 3.
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    (Original post by Louise_1988)
    Ok, having trouble with a different question if anyone can help.

    Find the sum of the integers, between 1 and 300 inclusive, not divisable by 3.

    Where do I start. Do i need an equation for a number not divisable by 3?

    Thanks

    Louise
    Don't you calculate the sum of all number sbetween 1 and 300 inclusive and then subtract the sum of the numbers divisable by 3 from the overall sum
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    (Original post by zazy)
    Don't you calculate the sum of all number sbetween 1 and 300 inclusive and then subtract the sum of the numbers divisable by 3 from the overall sum
    Yer, I think I will do that, seems so ovbious now it has been pointed out!!
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    (Original post by Louise_1988)
    Yer, I think I will do that, seems so ovbious now it has been pointed out!!
    W00t? That's what I said! I feel so unloved.
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    (Original post by Zapsta)
    W00t? That's what I said! I feel so unloved.
    Sorry, it was intended for you as well. I am very grateful.

    Please don't be sad...!!

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    (Original post by Zapsta)
    You need an equation for the sum of the numbers divisable by 3. You can then find out the sum of all the integers between 1 and 300 and subtract the some of the numbers divisable by 3.
    Did i say the same thing???*blushes out of embarrasment8 sorry
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    (Original post by zazy)
    Did i say the same thing???*blushes out of embarrasment8 sorry
    Its always useful to have a second opinion!!!
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    a possibly simpler method uses the concept that the proof of the arithmetic series uses and that is to group the numbers like so...

    (1 + 299) + (2 + 298) + (4 + 296) + ... + (149 + 151)

    Each individual sum adds up to 300 so all we need to know is how many there are. Well between 1 and 300, 200 numbers are not divisible by 3 so there are 100 pairs of integers as above. So the sum is 300 x 100 = 30000
 
 
 

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