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By what does the average of all odd numbers between 50 and 130 differ

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Joined: 29 Nov 2018
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By what does the average of all odd numbers between 50 and 130 differ  [#permalink]

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05 Mar 2019, 09:50
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35% (medium)

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74% (01:58) correct 26% (02:24) wrong based on 19 sessions

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By what does the average of all odd numbers between 50 and 130 differ from the average of all multiples of 3 between 20 and 160.

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Joined: 02 Aug 2009
Posts: 7437
Re: By what does the average of all odd numbers between 50 and 130 differ  [#permalink]

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05 Mar 2019, 21:08
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cfc198 wrote:
By what does the average of all odd numbers between 50 and 130 differ from the average of all multiples of 3 between 20 and 160.

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The solution can be found in different ways, BUT the point is to use the method that takes least time..

Average of odd number between 50 and 130, so the smallest is 51 and largest is 129..
Average will be $$\frac{51+129}{2}$$=90

Average of multiples of 3 between 20 and 160, so the smallest is 21 and largest is 159..
Average will be $$\frac{21+159}{2}$$=90

Thus difference is 90-90=0

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Re: By what does the average of all odd numbers between 50 and 130 differ  [#permalink]

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07 Mar 2019, 07:52
cfc198 wrote:
By what does the average of all odd numbers between 50 and 130 differ from the average of all multiples of 3 between 20 and 160.

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The average of all odd numbers between 50 and 130 is:

(51 + 129)/2 = 180/2 = 90

The average of all multiples of 3 between 20 and 160 is:

(21 + 159)/2 = 180/2 = 90

Thus, the difference is 0.

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Re: By what does the average of all odd numbers between 50 and 130 differ   [#permalink] 07 Mar 2019, 07:52
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