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What is the sum of all consecutive multiples of 8 between 400 and 600,

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What is the sum of all consecutive multiples of 8 between 400 and 600,  [#permalink]

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New post 28 Sep 2016, 02:54
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Re: What is the sum of all consecutive multiples of 8 between 400 and 600,  [#permalink]

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New post 28 Sep 2016, 04:42
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Bunuel wrote:
What is the sum of all consecutive multiples of 8 between 400 and 600, inclusive?

A. 8000
B. 10,400
C. 12,500
D. 13,000
E. 15,000


Hi
400 is 8*50 and 600 is 8*75...
Average of 400 and 600= 500, extreme multiples of 8..
# of multiples of 8 =75-50+1=26..

Sum =#*avg= 26*500=13000

D
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Re: What is the sum of all consecutive multiples of 8 between 400 and 600,  [#permalink]

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New post 28 Sep 2016, 04:49
total terms = 26 - [200/8 + 1]

sum = (400+600)/2 * 26 = 13000

Option D
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Re: What is the sum of all consecutive multiples of 8 between 400 and 600,  [#permalink]

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New post 28 Sep 2016, 04:52
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Its a series with a difference of 8 between two consecutive terms.

400/8 = 50th Terms

600/8 = 75th Terms.

Total no of terms = 75-50+1 = 26

Sum of all = n/2(First + last term)

= 26/2(400+600) = 13,000

Option D.
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Re: What is the sum of all consecutive multiples of 8 between 400 and 600,  [#permalink]

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New post 01 Mar 2017, 07:00
First term is 400 last term is 600. Difference is 8. n is total number of terms
Therefore 600 = 400 +(n-1)8 or n =26
Therefore the sum = n/2(first term +last term) = 26/2(400+600) =13000. Option D
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Re: What is the sum of all consecutive multiples of 8 between 400 and 600,  [#permalink]

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New post 01 Mar 2017, 11:28
Bunuel wrote:
What is the sum of all consecutive multiples of 8 between 400 and 600, inclusive?

A. 8000
B. 10,400
C. 12,500
D. 13,000
E. 15,000


400/8 = 50
600/8 = 75

Thus, there are 25 multiples of 8

Now, the series of numbers is { 400 , 408 , 416 ............ 584 , 592 , 600 }

Or , the sum of the series is 8 ( 50 + 51 + 52........ 73 + 74 + 75 }

Or , the sum of the series is 8 *1625 = 13000

Thus, answer must be (D) 13000
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Re: What is the sum of all consecutive multiples of 8 between 400 and 600,  [#permalink]

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New post 02 Mar 2017, 18:26
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Bunuel wrote:
What is the sum of all consecutive multiples of 8 between 400 and 600, inclusive?

A. 8000
B. 10,400
C. 12,500
D. 13,000
E. 15,000


We can determine the sum of all multiples of 8 between 400 and 600 inclusive using the following formula:

sum = average x quantity

The quantity is (600 - 400)/8 + 1 = 200/8 + 1 = 25 + 1 = 26.

Since we have a set of evenly spaced integers, we can calculate the average by using the following formula:

Average = (smallest multiple in the set + largest multiple in the set)/2. Thus:

Average = (400 + 600)/2 = 500

Thus, the sum is 500 x 26 = 13,000

Answer: D
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Re: What is the sum of all consecutive multiples of 8 between 400 and 600,  [#permalink]

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New post 18 Mar 2017, 13:10
n of multiplies: 600-400=200/8=25+1=26
26*(200+600)/2=1300
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Re: What is the sum of all consecutive multiples of 8 between 400 and 600, &nbs [#permalink] 18 Mar 2017, 13:10
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