Data Sufficiency Multiple Variables

[kkpatel1]

What is the value of C+B?

1) A+B=C+D=E+F

2) (E+F)=(D-B)


I performed this problem on a Kaplan Quiz. The answer explanation was not that great. If someone has a good way to solve this, it would be greatly appreciated.

OA: 3

[Testluv]

What is the value of C+B?

1) A+B=C+D=E+F

2) (E+F)=(D-B)


I performed this problem on a Kaplan Quiz. The answer explanation was not that great. If someone has a good way to solve this, it would be greatly appreciated.

OA: 3

Both statements are independently insufficient as you cannot derive the expression C+B from either of them, and so cannot ascertain the value of C + B.

Looking at them in combination:

Statement two tells us that D - B = E + F, and we know from statement one that E + F = A + B = C + D. Therefore:

D - B = E + F = A + B = C + D

Because the "D - B" is the oddball equation, we should work towards figuring something out about that. So, among the other equations, let's look at the equations that have "B" and "D" in them: A + B = C + D

Because A + B = C + D, if we subtract either from the other we will have zero. (When you subtract something from itself you have zero, eg: 5 - 5 = 0). Therefore:

(A + B) - (C + D) = 0

A + B - C - D = 0

A - C = D - B

We have successfully derived D - B, and we have learned that it is equal to A - C. But, among other things, we also know that D - B is equal to A + B. (We are focussing on A + B because, among the other equations, this is the equation that has the "B" term). Therefore:

A - C = D - B = A + B

Therefore:

A - C = A + B (if both A - C and A + B equal to D - B, then A - C and A + B are necessarily equal to each other).

Because A - C equals A + B, again, if we subtract one expression from the other we will have zero:

A + B - (A - C) = 0

A + B - A + C = 0

C + B = 0

The statements, while independently insufficient, are sufficient in combination. Choice C.

[gmatmachoman]

What is the value of C+B?

1) A+B=C+D=E+F

2) (E+F)=(D-B)


I performed this problem on a Kaplan Quiz. The answer explanation was not that great. If someone has a good way to solve this, it would be greatly appreciated.

OA: 3

USING 2)

C+D=D-B

-----> C+B=0

sO THE VALUE OF C+B =0.

Option C makes a logical answer.

[kkpatel1]

What is the value of C+B?

1) A+B=C+D=E+F

2) (E+F)=(D-B)


I performed this problem on a Kaplan Quiz. The answer explanation was not that great. If someone has a good way to solve this, it would be greatly appreciated.

OA: 3

Both statements are independently insufficient as you cannot derive the expression C+B from either of them, and so cannot ascertain the value of C + B.

Looking at them in combination:

Statement two tells us that D - B = E + F, and we know from statement one that E + F = A + B = C + D. Therefore:

D - B = E + F = A + B = C + D

Because the "D - B" is the oddball equation, we should work towards figuring something out about that. So, among the other equations, let's look at the equations that have "B" and "D" in them: A + B = C + D

Because A + B = C + D, if we subtract either from the other we will have zero. (When you subtract something from itself you have zero, eg: 5 - 5 = 0). Therefore:

(A + B) - (C + D) = 0

A + B - C - D = 0

A - C = D - B

We have successfully derived D - B, and we have learned that it is equal to A - C. But, among other things, we also know that D - B is equal to A + B. (We are focussing on A + B because, among the other equations, this is the equation that has the "B" term). Therefore:

A - C = D - B = A + B

Therefore:

A - C = A + B (if both A - C and A + B equal to D - B, then A - C and A + B are necessarily equal to each other).

Because A - C equals A + B, again, if we subtract one expression from the other we will have zero:

A + B - (A - C) = 0

A + B - A + C = 0

C + B = 0

The statements, while independently insufficient, are sufficient in combination. Choice C.

Thank you very much. That was very helpful. Got it!

[Testluv]

No problem!

You can get complex algebra problems that test your ability to manipulate expressions. However, gmatmachoman's approach was actually the best for this particular problem:

Because D - B = E + F, and because E + F = C + D, we can say:

C + D = D - B

C + B = D - D

C + B = 0

[Abdulla]

What is the value of C+B?

1) A+B=C+D=E+F

2) (E+F)=(D-B)


I performed this problem on a Kaplan Quiz. The answer explanation was not that great. If someone has a good way to solve this, it would be greatly appreciated.

OA: 3

C is the answer,

1) A+B=C+D=E+F INSUFF
2) E+F=D-B INSUFF

since E+F = C+D then substitute C+D for E+F

C+D=D-B
C+B =D-D
C+B = 0