OTC market codes

This topic has expert replies
Master | Next Rank: 500 Posts
Posts: 247
Joined: Sun Jul 27, 2008 1:39 am
Thanked: 2 times
GMAT Score:660

OTC market codes

by orel » Sun Nov 30, 2008 8:15 am
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. With of the following gives the maximum number of different stocks that can be designated with these codes?

2*26^5
26*26^4
27*26^4
26*26^5
27*26^5

In solving this problem I did the following: 26^4+26^5=27*26^4 it is the correct answer

But I don't know why did I do that....

Can anyone please explain.... Thanks
Source: — Problem Solving |

User avatar
Community Manager
Posts: 1049
Joined: Sun Apr 06, 2008 5:15 pm
Location: Pittsburgh, PA
Thanked: 113 times
Followed by:27 members
GMAT Score:710

by dmateer25 » Sun Nov 30, 2008 8:31 am
Think of each letter slot.

__ __ __ __

for a four letter code. Each slot can be 1 of the 26 letters in the alphabet.
so it would be 26*26*26*26=26^4




__ __ __ __ __

Same logic for the 5 letter code. Each slot can be 1 of the 26 letters in the alphabet.
26*26*26*26*26=26^5

So the max stocks would = 26^4+26^5 = 26^4(27)

Master | Next Rank: 500 Posts
Posts: 247
Joined: Sun Jul 27, 2008 1:39 am
Thanked: 2 times
GMAT Score:660

by orel » Sun Nov 30, 2008 9:33 am
thanks, dmateer25,

your explanation is really helpful!!!