DS - The Beat The GMAT Forum - Expert GMAT Help & MBA Admissions Advice

DS

Expert replies

SubratGmat2011: Junior | Next Rank: 30 Posts; Posts: 24; Joined: Mon Jul 05, 2010 11:35 pm; Thanked: 1 times

by SubratGmat2011 » Thu Sep 23, 2010 7:14 pm

In the number 1.4ab5, a and b represent single positive digits. If x = 1.4ab5, what is the value of 10 - x?

(1) If x is rounded to the nearest hundredth, then 10 - x = 8.56.

(2) If x is rounded to the nearest thousandth, then 10 - x = 8.564.

Like this post

Source: Beat The GMAT — Data Sufficiency | Thu Sep 23, 2010 7:14 pm

limestone: Master | Next Rank: 500 Posts; Posts: 307; Joined: Sun Jul 11, 2010 7:52 pmFollowed by: 1 member; Thanked: 36 times; GMAT Score:640

by limestone » Thu Sep 23, 2010 8:07 pm

1. x rounded to the nearest hundredth : x(rounded) =10 - 8.56 = 1.44
We can not know whether 1.4ab5 is rounded up or rounded down to 1.44
x can be either 1.4365 (round up) or 1.4415 (round down). => insuff

2. x is rounded to the nearest thousandth: x(rounded) = 10 - 8.564 = 1.436
1.4ab5 if rouded wil become 1.4a(b+1) (b+1 is consider 1 digit) and if b+1 = 10, then the thousandth digit will be 0, the hundredth digit a will be added 1.
However x(rounded) = 1.436 then b+1 = 6 then a = 3 ( if b+1 = 0, then a +1 =3))
Hence b = 6-1 =5, a =3, x= 1.4355 =>suff

Pick B, only 2 is suff.

"There is nothing either good or bad - but thinking makes it so" - Shakespeare.

Like this post

GMAT/MBA Expert

Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Thu Oct 10, 2019 5:25 am

SubratGmat2011 wrote:In the number 1.4ab5, a and b represent single positive digits. If x = 1.4ab5, what is the value of 10 - x?

(1) If x is rounded to the nearest hundredth, then 10 - x = 8.56.

(2) If x is rounded to the nearest thousandth, then 10 - x = 8.564.

Target question: What is the value of 10 - x?

Given: X = 1.4ab5

Statement 1: If x is rounded to the nearest hundredth, then 10 - x = 8.56
10 - 1.44 = 8.56
So, x rounded to the nearest HUNDREDTH = 1.44
So, x COULD equal 1.4355, 1.4365, 1.4375, 1.4385, 1.4395, 1.4405, 1.4415, 1.4425, 1.4435 OR 1.4445
Given all of the different possible values of x, 10 - x could have MANY different values.
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: If x is rounded to the nearest thousandth, then 10 - x = 8.564
10 - 1.436 = 8.564
In other words, x rounded to the nearest THOUSANDTH = 1.436
This tells us that a must equal 3, leaving us with 1.43b5
If 1.43b5 rounded to the nearest THOUSANDTH = 1.436, then b MUST equal 5
So, x must equal 1.4355, which means 10 - x MUST equal 8.5645
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer: B

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review