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If \(n + k = m,\) what is the value of \(k ?\)

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Source: — Data Sufficiency |

Gmat_mission wrote:
Thu May 21, 2020 1:21 am
If \(n + k = m,\) what is the value of \(k ?\)

(1) \(n = 10\)
(2) \(m + 10 = n\)

[spoiler]OA=B[/spoiler]

Source: Official Guide
Here's one approach...

Target question: What is the value of k?

Given: n + k = m

Statement 1: n = 10
Let's TEST some values
There are several values of m, n and k that satisfy statement 1. Here are two:
Case a: m = 12, n = 10, and k = 2. So, we have 10 + 2 = 12. In this case, k = 2
Case b: m = 13, n = 10, and k = 3. So, we have 10 + 3 = 13. In this case, k = 3
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: m + 10 = n
Take: m + 10 = n
Subtract 10 from both sides to get: m = n - 10
Rewrite as: m = n + (-10)
Rewrite as: n + (-10) = m
Add some color: n + (-10) = m
Compare this to the given information: n + k = m
From this, it is clear that k = -10
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer: B

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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