All of the stocks on the over the counter market are designated by either a 4 letter or a 5 letter code that is created by using the 26 letters of the alphabet. Which of the following gives the maximum number of different stocks that can be desgnated with these codes?
A. 2 (26)^5
B. 26(26)^4
C. 27(26)^4
D. 26(26)^5
E. 27(26)^5
OA is C
Do I need a special formula to solve this? An Expert.
GMAT MATH
This topic has expert replies
-
- Moderator
- Posts: 772
- Joined: Wed Aug 30, 2017 6:29 pm
- Followed by:6 members
-
- Master | Next Rank: 500 Posts
- Posts: 415
- Joined: Thu Oct 15, 2009 11:52 am
- Thanked: 27 times
Since you can use either a 4 letter symbol or a 5 letter symbol, you add the number of symbols for each.Roland2rule wrote:All of the stocks on the over the counter market are designated by either a 4 letter or a 5 letter code that is created by using the 26 letters of the alphabet. Which of the following gives the maximum number of different stocks that can be desgnated with these codes?
A. 2 (26)^5
B. 26(26)^4
C. 27(26)^4
D. 26(26)^5
E. 27(26)^5
OA is C
Do I need a special formula to solve this? An Expert.
Since the question doesn't say a letter can't be used more than once, you are free to use any of the 26 letters in each position.
So, the number of four letter symbols is 26*26*26*26 = 26^4
The number of 5 letter symbols is as above multiplied by one more 26, or 26^5.
Adding the two gives the correct answer 26^4 + 26^5. Notice that this is not among the correct answers. Don't give up hope.
Factor out the 26^4 and rewrite: 26^4(1+26) = [spoiler](26^4)*27, C[/spoiler]
GMAT/MBA Expert
- Scott@TargetTestPrep
- GMAT Instructor
- Posts: 7262
- Joined: Sat Apr 25, 2015 10:56 am
- Location: Los Angeles, CA
- Thanked: 43 times
- Followed by:29 members
We need to determine the maximum number of different stocks that can be designated by a 4-letter or a 5-letter code that is created by using the 26 letters of the alphabet.BTGmoderatorRO wrote:All of the stocks on the over the counter market are designated by either a 4 letter or a 5 letter code that is created by using the 26 letters of the alphabet. Which of the following gives the maximum number of different stocks that can be desgnated with these codes?
A. 2 (26)^5
B. 26(26)^4
C. 27(26)^4
D. 26(26)^5
E. 27(26)^5
OA is C
Do I need a special formula to solve this? An Expert.
Number of 5-letter codes:
26 x 26 x 26 x 26 x 26 = 26^5
Number of 4-letter codes:
26 x 26 x 26 x 26 = 26^4
Since the stocks can be designated by a 4-letter OR 5-letter code, we must add our results together to determine the maximum number of codes that can be created. We note that 26^4 is a common factor of both 26^5 and 26^4, so we have:
26^5 + 26^4 = 26^4(26 + 1) = 26^4(27)
Answer: C
Scott Woodbury-Stewart
Founder and CEO
[email protected]
See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews