It is currently 25 Mar 2019, 00:30

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# A number is randomly chosen from a list of 10 consecutive po

Author Message
TAGS:
GRE Prep Club Legend
Joined: 07 Jun 2014
Posts: 4857
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 105

Kudos [?]: 1783 [1] , given: 397

A number is randomly chosen from a list of 10 consecutive po [#permalink]  30 Jul 2018, 10:37
1
KUDOS
Expert's post
00:00

Question Stats:

77% (00:49) correct 22% (00:49) wrong based on 18 sessions
A number is randomly chosen from a list of 10 consecutive positive integers. What is the probability that the number selected is greater than the average (arithmetic mean) of all 10
integers?

A. $$\frac{3}{10}$$
B. $$\frac{2}{5}$$
C. $$\frac{1}{2}$$
D. $$\frac{7}{10}$$
E. $$\frac{4}{5}$$
[Reveal] Spoiler: OA

_________________

Sandy
If you found this post useful, please let me know by pressing the Kudos Button

Try our free Online GRE Test

GRE Instructor
Joined: 10 Apr 2015
Posts: 1543
Followers: 56

Kudos [?]: 1468 [1] , given: 8

Re: A number is randomly chosen from a list of 10 consecutive po [#permalink]  02 Aug 2018, 16:11
1
KUDOS
Expert's post
sandy wrote:
A number is randomly chosen from a list of 10 consecutive positive integers. What is the probability that the number selected is greater than the average (arithmetic mean) of all 10
integers?

A. $$\frac{3}{10}$$
B. $$\frac{2}{5}$$
C. $$\frac{1}{2}$$
D. $$\frac{7}{10}$$
E. $$\frac{4}{5}$$

We want to determine P(the number selected is greater than the average all 10 integers)

The average of all 10 integers = (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10)/10 = 55/10 = 5.5

So, we really want to determine P(selected number is greater than 5.5)
Let's see how many of the 10 integers are greater than 5.5
They are: 6, 7, 8, 9, and 10
There are 5 integers in total

So, P(selected number is greater than 5.5) = 5/10 = 1/2

Cheers,
Brent
_________________

Brent Hanneson – Creator of greenlighttestprep.com

GRE Prep Club Legend
Joined: 07 Jun 2014
Posts: 4857
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 105

Kudos [?]: 1783 [0], given: 397

Re: A number is randomly chosen from a list of 10 consecutive po [#permalink]  07 Aug 2018, 05:58
Expert's post
$$Explanation$$

In a list of 10 consecutive integers, the mean is the average of the 5th and 6th numbers.

Therefore, the 6th through 10th integers (five total integers) is greater than the mean. Since probability is determined by the number of desired items divided by the total number of choices, the probability that the number chosen is greater than the average of all 10 integers is $$\frac{5}{10} = \frac{1}{2}$$.

Another approach to this problem is to create a set of 10 consecutive integers; the easiest such list contains the numbers {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}. The mean is one-half the sum of the first element plus the last element, or $$\frac{10+1}{2}= 5.5$$.

Therefore, there are 5 numbers greater than the mean in the list: 6, 7, 8, 9 and 10. Again, the probability of choosing a number greater than the average of all 10 integers is $$\frac{5}{10} = \frac{1}{2}$$.
_________________

Sandy
If you found this post useful, please let me know by pressing the Kudos Button

Try our free Online GRE Test

Re: A number is randomly chosen from a list of 10 consecutive po   [#permalink] 07 Aug 2018, 05:58
Display posts from previous: Sort by