Is zw positive? (1) z + w^3 = 20 (2) z is positive

Answer: E
(I)Because Z & W will take following different values..
+,+
+,-
-,+
-,- Besides that we Z & W will follow any value in form of integer and non integer.. Insufficient

(II)statement doesn't say anything about W
Insufficient

(I) &(II) still we have two cases of +,-
+,+
Gives two different value for zw
Hence insufficient

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-,- scenario is not possible as per statement 1. We don't have to bother about integer and non-integer scenarios since we are concerned about their signs.

But still answer is E.


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IMO E

Statement 1 gives various possibilities Not Suff
Statement 2 doesn't tell anything about w. zw may or may not be positive Not Suff
Combining we still have 2 answers
Hence E

Question: Is zw > 0.

For this to be true z & w must have the same sign.

Statement 1: z + w^3 = 20

If z = - 7 & w = 3, then -7 + 3^3 = 20 or 20 = 20, but answer to the question is NO (z*w not positive)

If z = 12 & w = 2, then 12 + 2^3 = 20 or 20 = 20, Answer to the question is YES (z*w positive)

Not sufficient

Statement 2:

No mention about the value of "w" so insufficient.

Combining 1 & 2

If z = 21 & w = -1, then 21 + (-1)^3 = 20 or 20 = 20, but answer to the question is NO (z*w not positive)

If z = 19 & w = 1, then 19 + (1)^3 = 20 or 20 = 20, Answer to the question is YES (z*w positive)

Answer (E)
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IMO answer must be E.
For example if we take the below cases which satisfy both the conditions given in A and B:
z=21,w=-1 --> z+w^3 =21-1 =20 But zw= -ve
z=19,w=1 --> z+w^3 =19+1 =20 But zw= +ve
i.e. we are not getting a definite answer. Hence E.


~consider giving Kudos

@bunuel ooh yes.. -,- will finally yield +ve value.. True.. Thanks for feedback

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We need to determine whether the product of z and w is positive

Statement One Alone:

z + w^3 = 20

Using the information in statement one, we cannot determine whether the product of z and w is positive. For instance, if z = 12 and w = 2, the product of z and w is positive. However, if z = 28 and w = -2, then the product of z and w is negative. Statement one alone is not sufficient to answer the question. We can eliminate answer choices A and D.

Statement Two Alone:

z is positive

Using the information in statement two, we know that z is positive. However, since we don’t know anything about w, we cannot determine whether the product of z and w is positive. We can eliminate answer choice B.

Statements One and Two Together:

Using the information from statements one and two, we still cannot determine whether the product of z and w is positive. For instance, if z = 12 and w = 2, the product of z and w is positive. However, if z = 28 and w = -2, then the product of z and w is negative.

Answer: E
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Que, zw = + ve ?

1. z + w ^3 = 20
w = 1,2,3 ........ if w = 1 ^3 = 1 , 2^3 =8 , 3^3 = 27
if w = (-1)^3 = -1 , (-2) ^3 = -8
s0, zw can be +ve or -ve
not sufficient
2. z = +ve
w = 1,2,3 ........ if w = 1 ^3 = 1 , 2^3 =8 , 3^3 = 27
if w = (-1)^3 = -1 , (-2) ^3 = -8
zw can be +ve or -ve
not sufficient

E

Is zw positive?

(1) \(z + w^3 = 20\)

If w = -4, then z is positive. zw = negative
If w = 2, then z is positive. zw = positive

INSUFFICIENT.

(2) z is positive

No information about w; INSUFFICIENT.

(1&2) \(z + w^3 = 20\); z is positive

w can still be negative or positive, resulting in two different scenarios. INSUFFICIENT.

Answer is E.
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(1) \(12+(2)^3=20\); \(zw \) is positive

\(-7+(3)^3=20;\) \(zw \) is negative

Insufficient

(2) No information about \(w \) insufficient.

Considering both:
\(12+(2)^3=20;\) \(zw \) is positive

\(28+(-2)^3=20\); \(zw \) is negative

Insufficient.

The answer is E

Bunuel, here zw can have 2 different positive values....does it matter on the number of positive values obtained because the question here specifically asks whether zw is positive or not.

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