(A) which is a substance that promotes blood clotting, but not seriouslyinterfering
(B) a substance that promotes blood clotting, but not seriously interfering
(C) a substance that promotes blood clotting, but does not seriously interfere
(D) which is a substance to promote blood clotting, but does not seriouslyinterfere
(E) which is a substance that promotes blood clotting, but not a seriousinterference

Step 1) Identify this question as testing you on X&Y consistency framework. The keyword is “but”

Step 2) Notice the answer choice parts highlighted in red. To save time, you should be scanning these answer choices to find the pairs that match up.

Notice in (A) “promotes” does not go with “interfering”
(B) “promotes” does not go with “interfering”
(C) looks good
(D) “to promote” does not go with “interfere” (you need the word “to” again)
(E) “promotes” does not go with “interference”

So really, answer (C) is the only one that is possibly correct. Notice I didn’t even spend the time to reason through what makes sense and what doesn’t. I simply scanned the answer choices and found only one possibility that could potentially be the answer.

You could have answered this question in less than 10-15 seconds using this method. Of course it helps to go through some of the “does this make sense” thinking. But it’s also good exercise to try to answer questions in as little time as possible.

Other GMAT Questions and Explanations:
GMAT Math Ratio Word Problem
Last Minute GMAT Prep Plan
Goldman Analyst Compares GMAT Pill With ManhattanGMAT
GMAT Verbal Critical Reasoning Question

Hi Zeke,

I came acroos the following two problems, the two look similair but I think the approach is slightly different. Can you help me out please?

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Lap #	This Lap	Running Total

In a certain calculus class, the ratio of the number of mathematics majors to the number of students who are not mathematics majors is 2 to 5. If 2 more mathematics majors were to enter the class, the ratio would be 1 to 2. How many students are in the class?

(A) 10

(B) 12

(C) 21

(D) 28

(E) 35

So let’s break this down sentence by sentence.

OK, so what do we know from this info?
Let’s use x and y.
X = # of math majors.
Y = # of non-math majors.

So it says the ratio of math to non-math is 2:5.
Now translate that.
“# of math to non-math” = x/y
2:5 translates = 2/5

so
x          2
–   =    —-
y          5

Cross multiply and you get:
(Equation #1) 5x = 2y

Instead of (x/y), we now do ((x+2)/y)
Instead of (2/5), we now do (1/2)
x+2          1
—-    =   —–
y             2

Cross Multiply and you get:
2(x+2) = 1(y)
(Equation #2) 2x + 4 = y
Combine this with (Equaiton #1) 5x=2y from above.
Notice (Equation 1) is 2y, which is twice the total amount in (Equation #2).
So all you have to do is double (Equation #2) so it matches (Equation #1).

2x +4 = y
becomes
4x + 8 = 2y
And equation (1) is 5x = 2y.

4x + 8 = 5x
8= x
x= 8
Now plug in x into (2x+4) = y; (2(8)+4) = 20 = y

So x = 8 and y = 20.
The total number of students is # of math + # of non-math, which is x + y = 8 + 20 = 28

So that’s an answer choice D. Voila!