Math!! arghh

[Blazeherd2306]

Can anyone solve these? They're extra credit problems for my precalc class, and I think if I do them I could boost my grade up to an A....

Find the sum of the reciprocals of two real numbers, given that these two numbers have a sum of 50 and a product of 25.

I have no clue on this one. I tried using a system of equations, but it didn't really work out to suit what the problem is asking

A typical telephone number in the United States used to be 7 digits. Recently, several areas of the country have started using ten-digit telephone numbers. Columbus, Georgia and Orlando, Florida are two such cities. If the entire country goes to a ten-digit telephone, exactly how many different ten-digit telephone numbers will be available such that the first digit cannot be a 0 or 1 and the fourth digit cannot be a 0 or a 1?

I think this can be solved using combinatorics or permutations...one of them. I'm not completely sure though.

[rich311k]

not sure on the first but the second is 8 * 10 * 10 * 8 *10 *10 * 10 * 10 * 10 * 10 = 6,400,000,000

[Blazeherd2306]

I already got the first one.

Thanks Rich!

[Devilishturtles]

Can't help you, but I thought every city in the country now had 10 digit telephone numbers? Or is your question just an old question?
Sorry for the hijack

[Blazeherd2306]

Must've been an old question...