Math Expert
Joined: 02 Sep 2009
Posts: 50060

Rounding Up Some Official GMAT Questions!
[#permalink]
Show Tags
29 Apr 2015, 04:25
FROM Veritas Prep Blog: Rounding Up Some Official GMAT Questions!

Last week we looked at some rounding rules. Today, let’s go over some official questions on rounding. They are quite simple and if we just keep the “Slip to the side and look for a 5” rule in mind, they can be easily solved.
Question 1: If n = 2.0453 and n* is the decimal obtained by rounding n to the nearest hundredth, what is the value of n* – n?
(A) 0.0053
(B) 0.0003
(C) 0.0007
(D) 0.0047
(E) 0.0153
Solution: A quick note on place value nomenclature:
Given a decimal 345.789, we know that 5 represents the units digit, 4 the tens digit and 3 the hundreds digit. Also, 7 represents the tenths digit, 8 the hundredths digit and 9 the thousandths digit and so on…
Now let’s go back to this question:
n = 2.0453
We need to round n to the nearest hundredth which means we will retain 2 digits after the decimal. The third digit after the decimal is 5 so 2.0453 rounded to the nearest hundredth is 2.05.
Thus n* – n = 2.05 – 2.0453 = 0.0047
Answer (D)
Question 2: If digit h is the hundredths digit in the decimal n = 0.2h6, what is the value of n, rounded to the nearest tenth?
Statement 1: n < 1/4
Statement 2: h < 5
Solution: Given that n = 0.2h6
We need to find the value of n rounded to the nearest tenth i.e. we need to keep only one digit after the decimal.
Statement 1: n < 1/4
In decimal form, it means n < 0.25
If h were 5 or greater, n would become 0.256 or 0.266 or higher. All these values would be more than 0.25 so h must be less than 5 such as 0.246 or 0.236 etc. In all such cases, n would be rounded to 0.2
This statement alone is sufficient.
Statement 2: h < 5
This is even simpler. Since we have been given that h is less than 5, when we round n to the tenths digit, we will get 0.2
This statement alone is also sufficient.
Answer (D)
Question 3: If d denotes a decimal number, is d >= 0.5?
Statement 1: When d is rounded to the nearest tenth, the result is 0.5.
Statement 2: When d is rounded to the nearest integer, the result is 1.
Solution: Again, a simple question!
We need to find whether d is greater than or equal to 0.5 or not.
Statement 1: When d is rounded to the nearest tenth, the result is 0.5.
This means that whatever d is, when we round it to the nearest tenth, we get 0.5. What are the possible values of d? If d is anywhere from 0.450 to 0.5499999…, it will be rounded to 0.5
Some of these numbers are less than 0.5 and others are greater than 0.5 so this statement alone is not sufficient.
Statement 2: When d is rounded to the nearest integer, the result is 1.
In this case d must be at least 0.5; only then can it be rounded to 1.
d can be anything from 0.50 to 1.499999… In any case, d will be greater than or equal to 0.5.
This statement alone is sufficient to answer the question.
Answer (B)
We hope you see that if we just remember the rules, we can solve most rounding questions very quickly and efficiently.
Karishma, a Computer Engineer with a keen interest in alternative Mathematical approaches, has mentored students in the continents of Asia, Europe and North America. She teaches the GMAT for Veritas Prep and regularly participates in content development projects such as this blog!

ForumBlogs  GMAT Club’s latest feature blends timely Blog entries with forum discussions. Now GMAT Club Forums incorporate all relevant information from Student, Admissions blogs, Twitter, and other sources in one place. You no longer have to check and follow dozens of blogs, just subscribe to the relevant topics and forums on GMAT club or follow the posters and you will get email notifications when something new is posted. Add your blog to the list! and be featured to over 300,000 unique monthly visitors
_________________
New to the Math Forum? Please read this: Ultimate GMAT Quantitative Megathread  All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
Collection of Questions: PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.
What are GMAT Club Tests? Extrahard Quant Tests with Brilliant Analytics
