Variables in the Answer Choices

[DBushkalov]

Hi guys,

just finished the chapter of [60-Day Study Guide] Day 14 - Word Problems III - Variables in the Answer Choices and Minor Question Types".

Regarding the trick the MANHATTAN GMAT Strategy guide gives you, you should use numbers in such questions and then simply replace with those numbers the variables in the answer choices:

Step 1: Identify unknowns and replace them with numbers.

Step 2: Use these numbers to calculate the answer to the problem,

Step 3: Plug the same numbers into the answer choices (and choose the one that yields your number)


However, there are certain tasks where the numbers are agonizingly close. For example, take task 198 from OG 13-th edition (the task about newspapers)

Using carefully selected numbers I have 20% for p (so, p=20). This leads to a value of 16,67 % for r (r=16,67). Although r is not a good looking number it is tough to actually find good numbers for both, P and R. Anyway, after i did this, i had to replace P in the answer choices with 50 and just see which answer would yield a number around 16,5.

To my surprise the answers are extremely close.

Answer A: 19 (so far so good)

Answer B: 13 (still o.k.)

Answer C: 16,9 (now that's extremely close, and you have already lost significant amount of time solving the task and doing these pretty heavy computations)

Answer D: CORRECT

Answer E: 16,5 (insanely close to the correct answer, 16,6. Had E been before D, this one would have been an awful choice to make on a real exam)



Furhermore, regarding task 181: " If m>0 and x is m percent of y, then, in terms of m, y
is what percent of x ? "

Here I choose y=100, m is 10% (m=10) and i get for x=10 too.

Therefore y = 1000% * X. We are looking for the answer that would yield 1000 when we replace m with the value we picked for M, namely, m=10.

Answer A: 100*m (this equals 1000 and is thus correct)

Answer E: 10,000/ m (this equals 10,000/ 10, which is also 1000)

Now, after having lost over a minuite to solve this task you actually get 2 correct answers. You have no more time to solve it, so just pick one and keep on. But this exam is not about guessing, isn't it ?

Therefore I would like to ask for a better technique to solve such tasks, in which you have variable in the answer choices and in the question of itself.


Thanks a lot in advance

[GMATGuruNY]

r)
However, there are certain tasks where the numbers are agonizingly close. For example, take task 198 from OG 13-th edition (the task about newspapers)

Check my two posts here:

https://www.beatthegmat.com/struggling-w ... 20100.html

[GMATGuruNY]

If m > 0 and x is m percent of y, then, in terms of m, y is what percent of x?

(A) 100m
(B) 1/100m
(C) 1/m
(D) 10/m
(E) 10,000/m

Let m=200 and y=10.
Since x is m% of y, x = 200% of 10 = 20.
Since y=10 and x=20, y/x = 10/20 = 50%. This is our target.

Now we plug m=200 into the answer choices to see which yields our target of 50%.
Only E works:
10,000/200 = 50.

The correct answer is E.