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

Question

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

Bunuel · Answer

SOLUTION

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

n + k = m ;
 k=m-n=?

(1) n = 10 -->  k=m-n=m-10 . Not sufficient.

(2) m + 10 = n -->  m-n=-10 , so  k=-10 . Sufficient.

Answer: B.

SOURH7WK · Answer

IMO B
n+k=m, Find K
ie m-n = k
St 2: Sufficient: m+10=n ie m-n=-10=k
St 1: Insufficient. n=10, we don't know the value of either m or k

feellikequitting · Answer

For Statement 1: N=10

10+K=M, (K&M, are too many #'s, NOT SUFF)

For Statement 2: M+10=N
 -10 -10 (subtract -10 on each side)
 M = N-10 
 -N -N (subtract N, to Isolate M & N)
 M-N = -10 This is can be solved.

Statement 2: SUFF:

ScottTargetTestPrep · Answer

We are given that n + k = m, and we need to determine the value of k. Since we know that n + k = m, we know that k = m – n. Thus, if we determine a value for m – n, we will know the value of k.

Statement One Alone:

n = 10

Although we know that n = 10, without knowing the value of m, we cannot determine the value of k. Statement one alone is not sufficient. We can eliminate answer choices A and D.

Statement Two Alone:

m + 10 = n

Manipulating statement two we get:

m + 10 = n

m – n = -10

Since we know that m – n = -10, we know that k = -10. Statement two alone is sufficient.

The answer is B.

CrackverbalGMAT · Answer

This is an easy question on simple equations. From the question stem, we know that n+k = m.  Since we are finding the value of k, we will try to express k in terms of the other variables  i.e.

k = m -n

From this, it’s clear that we need the value of m-n, to find the value of k.

From statement I alone, n = 10. Since we do not have the value of m, statement I alone is insufficient. 
Answer options A and D can be eliminated, the possible answer options are B, C or E.

From statement II alone, m + 10 = n. Therefore, m = n – 10. Substituting this in the equation for k, we have, 
k = n – 10 – n = -10. This is a definite value for k.

Statement II alone is sufficient to find a unique value for k. Answer options C and E can be eliminated since statement II is sufficient when taken individually.
 The correct answer option is B .

In a DS question on equations, the variable whose value we are trying to calculate should always be kept on the LHS while everything else can be transferred to the RHS (this is a good practice in general too for all DS questions). This will give you a very clear idea of what data you have to look for, in the statements, to be able to solve the question.

Hope that helps!

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

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GMAT Data Sufficiency (DS) Questions

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