This problem can be solved as a simple word problem in which we must convert words to math. Before we create our equations, we want to define some variables.

J = Jake’s current weight, in pounds

S = Sister’s current weight, in pounds

We are told that “If Jake loses 8 pounds, he will weigh twice as much as his sister." We put this into an equation:

J – 8 = 2S

We can isolate J by adding 8 to 2S:

J = 2S + 8 (Equation 1)

Next, we are told that “Together they now weigh 278 pounds.” We can also put this into an equation.

J + S = 278 (Equation 2)

To solve this equation, we can substitute 2S + 8 from Equation 1 for the variable J in Equation 2:

2S + 8 + S = 278

3S = 270

S = 90

We now know that the sister weighs S = 90 pounds, and we can plug that value into either equation to determine J. Let’s plug 90 for S into equation 2:

J + 90 = 278

J = 188

Answer: E
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(x-8) = 2s

s+x = 278 --> s= 278-x

x-8 = 2(278-x)

3x=564

x=188

Hi All,

This question can be solved with fairly straight-forward Algebra (as the other solutions have proven). It can also be solved by TESTing THE ANSWERS and a bit of logic.

We're told that the total weight of Jake and his sister is 278 pounds. We're also told that if Jake lost 8 pounds, then he would weight TWICE as much as his sister. This means that, right now, Jake weighs MORE than TWICE his sister. We're asked for Jake's current weight.

Since Jake weighs more than twice his sister, his weight is MORE than 2/3 of the 278 pounds. Looking at these answer choices, I would TEST one of the bigger values first... Under normal circumstances, that would be Answer D. With a quick estimate though we can see that 2/3 of 270 pounds would be 180 pounds, but Jake has to weight MORE than that, so I'm going to TEST Answer E first....

If Jake weights 188 pounds...
Jake - 8 = 180 pounds....
Sister = 90 pounds
90 + 180 + 8 = 278 pounds
This is a MATCH for the information in the prompt, so Jake MUST weight 188 pounds.

Final Answer:

GMAT assassins aren't born, they're made,
Rich
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let Jack's Weight be J
His sister weight be S
J-8 = 2S ----1
J+S = 278 ---2
Then,
J= 2S+8
2S+8+S = 278
S= 270/3
S=90
then J = 188
Answer is E

Here's a solution that uses one variable.

Let x = Jake's present weight in pounds
So, x - 8 = Jake's hypothetical weight IF he were to lose 8 pounds

If Jake loses 8 pounds, he will weigh twice as much as his sister.
In other words, the sister weighs HALF as much as Jake's hypothetical weight of x - 8 pounds
So, (x - 8)/2 = sister's present weight

Together they NOW weigh 278 pounds.
So, Jake's present weight + sister's present weight = 278
So, x + (x - 8)/2 = 278
Eliminate the fraction by multiplying both sides by 2 to get: 2x + (x - 8) = 556
Simplify: 3x - 8 = 556
Add 8 to both sides: 3x = 564
Solve: x = 564/3 = 188

Answer: E

Cheers,
Brent
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I loved it how FANewJersey has put this question in, option E is indeed pretty far from others and if hard pressed on time such a trick can indeed be really handy

Even-8=Even
Even+2*Even= 278 (Even)

Well, we need an Even. Only E.

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Hi Asad,

YES - the Number Properties that you've described could be used to correctly answer this question. This goes to show how important it is to pay attention to how the answers are written. There are plenty of circumstances (in BOTH the Quant and Verbal sections), in which you can use the 5 answer choices "against" the prompt to logically eliminate the wrong answers and zero-in on the correct one.

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