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

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Senior SC Moderator
Joined: 14 Nov 2016
Posts: 1315
Location: Malaysia
If ab=4, what is the value of abc? (1) bc=2 (2) ca=8  [#permalink]

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19 May 2017, 01:29
2
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Difficulty:

45% (medium)

Question Stats:

66% (01:28) correct 34% (02:07) wrong based on 48 sessions

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

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

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Joined: 22 Aug 2013
Posts: 1348
Location: India
Re: If ab=4, what is the value of abc? (1) bc=2 (2) ca=8  [#permalink]

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19 May 2017, 02:22
3
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.

SVP
Joined: 26 Mar 2013
Posts: 1837
Re: If ab=4, what is the value of abc? (1) bc=2 (2) ca=8  [#permalink]

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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

Manager
Joined: 13 Mar 2013
Posts: 167
Location: United States
GPA: 3.5
WE: Engineering (Telecommunications)
Re: If ab=4, what is the value of abc? (1) bc=2 (2) ca=8  [#permalink]

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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

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