Hi Nina1987,

Having a strong 'instinct' can be beneficial on Test Day, but you have to focus more on proving that you're correct. The work involved in many DS questions is relatively simple algebra/arithmetic, so rather than trying to 'talk your way past' a prompt, do the necessary work to PROVE what the correct answer is. In this prompt, you can TEST VALUES and quickly prove the correct answer in under a minute.

GMAT assassins aren't born, they're made,
Rich

sanyalpritish wrote:What is the value of v³ - k³ ?
(1) vk > 0
(2) v - k = 6

Target question: v³ - k³?

Statement 1: vk > 0
This statement doesn't FEEL sufficient, so I'll TEST some values.
There are several values of v and k that satisfy statement 1. Here are two:
Case a: v = 1 and k = 1, in which case v³ - k³ = 1³ - 1³ = 0
Case b: v = 2 and k = 1, in which case v³ - k³ = 2³ - 1³ = 7
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Aside: For more on this idea of plugging in values when a statement doesn't feel sufficient, you can read my article: https://www.gmatprepnow.com/articles/dat ... lug-values

Statement 2: v - k = 6
This statement doesn't FEEL sufficient either, so I'll TEST some values.
There are several values of v and k that satisfy statement 2. Here are two:
Case a: v = 7 and k = 1, in which case v³ - k³ = 7³ - 1³ = some big number
Case b: v = 8 and k = 2, in which case v³ - k³ = 8³ - 2³ = a DIFFERENT big number
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

NOTE: I'm not going to waste time calculating 7³ - 1³ and 8³ - 2³. A see that they evaluate to be different values, which means I can't answer the target question. That's all I need to know.

Statements 1 and 2 combined
NOTICE that the numbers I tested for statement 2 ALSO satisfy statement 1. We have:
Case a: v = 7 and k = 1, in which case v³ - k³ = 7³ - 1³ = some big number
Case b: v = 8 and k = 2, in which case v³ - k³ = 8³ - 2³ = a DIFFERENT big number

Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT

Answer = E

Cheers,
Brent