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If ab=4, what is the value of abc? (1) bc=2 (2) ca=8

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If ab=4, what is the value of abc? (1) bc=2 (2) ca=8 [#permalink]

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New post 19 May 2017, 01:29
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A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

63% (01:03) correct 37% (01:28) wrong based on 46 sessions

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If ab=4, what is the value of abc?

(1) bc=2
(2) ca=8

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Re: If ab=4, what is the value of abc? (1) bc=2 (2) ca=8 [#permalink]

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New post 19 May 2017, 02:22
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Product ab is already given. To find the product abc, we need to know the value of c.

Statement 1. Product bc is given, but we cannot say anything specific about c. Insufficient.

Statement 2. Product ca is given, but we cannot say anything specific about c. Insufficient.

Combining the two statements: Now we can multiply both equations:
bc * ca = 2*8
abc^2 = 16

Substituting the value of ab here,
4c^2 = 16 or c^2 = 4
This still gives two values of c: 2 and -2.
So Insufficient.

Answer is E.
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Re: If ab=4, what is the value of abc? (1) bc=2 (2) ca=8 [#permalink]

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New post 19 May 2017, 06:05
If ab=4, what is the value of abc?

(1) bc=2

Multiply both equations..... a c b^2 =8

No way to get abc.........Insufficient

(2) ca=8

Multiply both equations..... b c a^2 =32

No way to get abc.........Insufficient

Combining 1 & 2

Multiply 3 equations:

a^2 b^2 C^2 = 64.................(a b c)^2= 64

abc = 8 or abc =-8

Insufficient

Answer: E
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Re: If ab=4, what is the value of abc? (1) bc=2 (2) ca=8 [#permalink]

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New post 21 May 2017, 05:45
If ab=4, what is the value of abc?

(1) bc=2

Multiply both equations..... a c b^2 =8

No way to get abc.........Insufficient

(2) ca=8

Multiply both equations..... b c a^2 =32

No way to get abc.........Insufficient

Combining 1 & 2

Multiply 3 equations:

a^2 b^2 C^2 = 64.................(a b c)^2= 64

abc = 8 or abc =-8 ( Be careful here , its square of abc . Therefore , value of abc can be both positive or negative . Which we are not sure )

Hence not

Insufficient

Answer: E


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Re: If ab=4, what is the value of abc? (1) bc=2 (2) ca=8   [#permalink] 21 May 2017, 05:45
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If ab=4, what is the value of abc? (1) bc=2 (2) ca=8

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