GMAT Problem Solving POE – Broad Range

What worries GMAT test takers in Problem Solving is the lengthy calculations, and translation of statements to equations. Lot of students prefers the use of calculators. If you have started solving a few GMAT PS questions, you might have realized that solving some of the toughest GMAT 800 questions does not require even solving them in a traditional manner. Process of Elimination is an often-neglected technique when it comes to solving time consuming and tricky GMAT Problem solving questions.

In this article, we will cover how to classify answer choices into groups, and guess the probable range of the answer based on the facts provided in the question. In order to be successful with this strategy, find out how many answers are close to each other in value. Group them together, and then start with data substitution.

Let us look at an example:

Q) Tim and Phil together can complete the flooring on 2nd floor in 6 days. When Phil was on leave, Tim completed a similar flooring job in 18 days. How long will Phil take to complete flooring on 2nd Floor if Tim is unavailable.

a) 12 days
b) 22 days
c) 18 days
d) 7 days
e) 9 days

Answer

Although the question tries to mask the facts, if you read it carefully, the question is simple – what is the rate of completing flooring for Phil if Phil and Tim can do the task together in 6 days, and Tim alone can do the same task in 18 days.

Now if you look at the answer choices, the answers are in a broad spectrum. Classify the answer choices into Groups:

Group 1 = {7, 9, 12}
Group 2 = {18, 22}

You cannot predict whether the answer choice will be from Group 1 and Group 2 just based on the number of answer choices in each group but if you have read the facts.

Fact 1:  Job Done together takes 6 Days
Fact 2: Job Done by Tim Alone takes 18 days

Clearly, Phil has to compensate Tim’s poor workmanship to meet the 6 Days completion rate.

Phil must complete the work in less than 18 days but more than 6 days

Range:  6-18 days.

Only Group 1 satisfies that range. Eliminate Group 2 or answer choices B and C

A Simple formula substitution shows that

1/t + 1/p = 1/10

1/20 + 1/p = 1/10

1/p =1/6 – 1/18

1/p= 12/108

P = 9 Days

Correct Answer: D

You might ask why you have to think about the range of answers and groups. We have seen GMAT test takers making careless mistakes. When you know the probable and improbable range, these kinds of careless mistakes can be avoided.