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# The average of a and b is 70. The average of a and c is 100. What is b

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Math Expert
Joined: 02 Sep 2009
Posts: 58458
The average of a and b is 70. The average of a and c is 100. What is b  [#permalink]

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21 Jan 2019, 00:59
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25% (medium)

Question Stats:

89% (01:00) correct 11% (00:41) wrong based on 12 sessions

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The average of a and b is 70. The average of a and c is 100. What is b – c?

A –60
B –30
C 15
D 30
E 60

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Re: The average of a and b is 70. The average of a and c is 100. What is b  [#permalink]

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21 Jan 2019, 01:27
a+b = 140.........(1)
a+c = 200..........(2)
(1)-(2) = -60

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Re: The average of a and b is 70. The average of a and c is 100. What is b  [#permalink]

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21 Jan 2019, 04:31
Bunuel wrote:
The average of a and b is 70. The average of a and c is 100. What is b – c?

A –60
B –30
C 15
D 30
E 60

a + b/2 = 70

a + b = 140.

again,

a + c / 2 = 100

a + c = 200

a + b = 140
a + c = = 200
.........................................
b - c = -60...............................deducting second from the first one.

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Re: The average of a and b is 70. The average of a and c is 100. What is b  [#permalink]

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21 Jan 2019, 08:11
Bunuel wrote:
The average of a and b is 70. The average of a and c is 100. What is b – c?

A –60
B –30
C 15
D 30
E 60

a+b= 140
a+c=200

a+b-a-c = 140-200
= -60
IMO A
Re: The average of a and b is 70. The average of a and c is 100. What is b   [#permalink] 21 Jan 2019, 08:11
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