Permutations Problem

each letter can take 122 different signs.
total ways of forming 2 letters is 122*122

Now if the company wants to use 124 signs, then for 2 letters ,
total number of ways = 124*124.

Difference= (124)^2 - (122)^2
= (124+ 122) (124-122)
= 246*2 => 492 additional area codes can be created.

Answer = C

I am not able to figure out, how you got 122*122? can you please elaborate?

Is it because, you have 122 signs for the first letter and for each of the 122 letters you can have further 122 signs right?

To make it simple, let's say you have only 3 symbols (assume a, b, c) if you have two letter code then you have:

aa ba ca
ab bb cb
ac bc cc

Thus, 3 * 3 = 9 ways.

I thinking I am getting it, Am I correct?[/img]

exactly.
for the first letter- you have 3 ways.(a, b, c)
and for the next letter similiar 3 ways.
so total 3*3 ways.

Hope i have clarified ur doubt!

Yes, sir you have. Thank you so much.

fibbonnaci wrote:exactly.
for the first letter- you have 3 ways.(a, b, c)
and for the next letter similiar 3 ways.
so total 3*3 ways.

Hope i have clarified ur doubt!