Three numbers p, q and r are all prime numbers less than 50 with the property that . How many values of r are possible?

I would think this is 0 because prime numbers have to be odd and odd + odd always equals an even number. But the answer is not 0

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- July 28th 2009, 11:52 PMjgv115Question
Three numbers p, q and r are all prime numbers less than 50 with the property that . How many values of r are possible?

I would think this is 0 because prime numbers have to be odd and odd + odd always equals an even number. But the answer is not 0 - July 29th 2009, 12:21 AMSENTINEL4
It's not all prime numbers odd. You forget 2 which is prime and even.

Then if p=2 and q=3 then p+q=2+3=5=r and p,q,r are all primes.

Same if p=2 and q=5 then r=7.

Check if there are any more... - July 29th 2009, 12:25 AMjgv115
wow forgot about 2...

ok

2,3

2,5

2,11

2,17

2,29

2,41

did i miss any? - July 29th 2009, 12:28 AMjgv115
OK I have another one.

When 1000^2008 is written as a numeral, the number of digits written is..

How do you go about doing this? - July 29th 2009, 12:35 AMSENTINEL4
I don't quite understand what you want for the last one you asked

You want to know how many digits this number has?? Too many! (Rofl) - July 29th 2009, 12:36 AMsongoku
1000^1 = 1000 ( 4 digits)

1000^2 = 1,000,000 (7 digits)

1000^3 = 1,000,000,000 (10 digits)

there is pattern ^^ - July 29th 2009, 01:11 AMjgv115
oo alright! so if has 7 digits (6 zeros) that means

(the extra 1) is 6025!