Averages of three sets A,B and C containing positive numbers : DS Archive
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# Averages of three sets A,B and C containing positive numbers

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Averages of three sets A,B and C containing positive numbers [#permalink]

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19 Jul 2006, 14:30
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Averages of three sets A,B and C containing positive numbers are x,y, and z.
Is the combined average of all elements of A,B and C is greater than 15?

1. x = 10 and y = 17
2. x = 10 and z > y > x
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Re: DS: Averages of Sets [#permalink]

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19 Jul 2006, 15:03
E.

the combined average of all elements of A, B and C = (MX + NY + KZ)/(M+N+K), where m,n and k are no of elements in a, b, and c respectively.

is (MX + NY + KZ)/(M+N+K)>15?

1. we donot know z amd the number of elements in each set. NSF
2. also donot know about x, y and z. NSF

from 1 and 2, we know that z (>17) > y (17) > x (10). still we miss number of elements in each set or their ratios/proportions. insuff
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20 Jul 2006, 01:56
E.

Lets say each set only contains 1 integer.

1) x= 10 y =17
Let set c contain positive integer 1. Hence z =1
Total average = 10+17+1/3 = 33
Similarily it can be shown that average > 15
Not suff

2) x= 10 and z>y>x
Let y be 11 and z be 12
Total av = 10+11+12/3 =11
Similarily it can be shown that total av > 15

Together.
x=10 y=17 and z > y
Let z be 18
Then total av = 10+17+18/3 = 15
Hence together the total av can be >= 15 not only > 15
Not suff.
20 Jul 2006, 01:56
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