November 14, 2018 November 14, 2018 07:00 PM PST 08:00 PM PST Join the webinar and learn timemanagement tactics that will guarantee you answer all questions, in all sections, on time. Save your spot today! Nov. 14th at 7 PM PST November 15, 2018 November 15, 2018 10:00 PM MST 11:00 PM MST EMPOWERgmat is giving away the complete Official GMAT Exam Pack collection worth $100 with the 3 Month Pack ($299)
Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 50544

Question Stats:
52% (01:19) correct 48% (01:33) wrong based on 86 sessions
HideShow timer Statistics



Math Expert
Joined: 02 Sep 2009
Posts: 50544

Re M1912
[#permalink]
Show Tags
16 Sep 2014, 00:05
Official Solution:An electronic clock shows time in hours and minutes. For example, 08:15 means that it is now a quarter past eight. If one looks at the clock at some time between 6:00 and 9:00, what is the probability that he will see the digit 8 ? A. \(\frac{1}{5}\) B. \(\frac{1}{3}\) C. \(\frac{2}{5}\) D. \(\frac{4}{9}\) E. \(\frac{1}{2}\) The period between 6:00 and 9:00 consists of 180 minutes. During 72 minutes of these 180 the clock will display the digit 8: during 60 minutes of the 8:009:00 hour and during 6 minutes of each of the hours 6:007:00 and 7:008:00 (for example, between 6:00 and 7:00 the clock will show digit 8 only at 06:08, 06:18, 06:28, 06:38, 06:48, and 06:58). The required probability \(= \frac{72}{180} = \frac{2}{5}\). Answer: C
_________________
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



Current Student
Joined: 03 May 2015
Posts: 11

Re M1912
[#permalink]
Show Tags
22 May 2016, 02:17
I think this is a highquality question and I agree with explanation. We need to mention " both inclusive" after 6 to 9 in the question ; else denominator may become less than 180 as 6:00 and 9:00 are not included.



Senior Manager
Joined: 31 Mar 2016
Posts: 386
Location: India
Concentration: Operations, Finance
GPA: 3.8
WE: Operations (Commercial Banking)

Re M1912
[#permalink]
Show Tags
09 Jul 2016, 07:33
I think this is a highquality question and I agree with explanation. Superb.



Current Student
Joined: 20 Oct 2014
Posts: 38

Re: M1912
[#permalink]
Show Tags
21 Jul 2016, 10:57
This question is a good candidate for calculated guessing. From 6:00 to 8:59, at least 1 hour out of the total 3 hours has a 8. So we are looking for a number more than 1/3 or 33%. Hence, options (a) and (b) are out. Options c,d and e translate to 40%, 44% and 50%. Since the number 8 appears very few times in a hour, option (c) must be our best guess.



Intern
Joined: 04 Aug 2014
Posts: 29
GMAT 1: 620 Q44 V31 GMAT 2: 620 Q47 V28
GPA: 3.2

Re: M1912
[#permalink]
Show Tags
27 Mar 2017, 23:13
hi brunel,
i am unable to understand the point how digit 8 will appear 60 times from time interval 8:00 to 9:00.As per me 8:08 , 8:18 , 8:28 etc will give 8 6 times + 59 times on the hour digit.
kindly clear where i am going wrong
thanks in advance



Math Expert
Joined: 02 Sep 2009
Posts: 50544

Re: M1912
[#permalink]
Show Tags
28 Mar 2017, 00:26



Intern
Joined: 09 Mar 2017
Posts: 1

Re: M1912
[#permalink]
Show Tags
10 Aug 2017, 10:57
By my math, there are 179 minutes between 6:00 and 9:00. Anyone else getting caught up on that? Yes, it's technical and relatively immaterial.



Manager
Joined: 09 Oct 2016
Posts: 89
Location: United States
GPA: 3.49

Re: M1912
[#permalink]
Show Tags
24 Aug 2017, 05:43
Well apparently my rushed mind thinks there are 360 minutes in three hours...
Anyway this is a high quality question.



Manager
Joined: 31 Oct 2016
Posts: 108

Re: M1912
[#permalink]
Show Tags
06 Dec 2017, 06:39
The very best approach for this types of questions is an estimation. There are only 3 hours. The probability of seeing 8 is 1/3 plus another 12 cases. Slightly more than 1/3. 2/5 fits best.










