Hello lads. So I did my senior maths challenge today, and there was a question which struck me as being difficult. I even asked my maths teacher and he couldn't solve it as fast as he could. So who can run me through how you would solve the following:
abcd + abc + bcd + acd + abd + ab + bc + cd + ad + ac + bd+ a + b + c + d = 2009
Find a+b+c+d
Anyone got any idea how to do this?
Yeah it sayd that a b c and d are positive integers.
Also this might help, the answer is one of the following:
A)73 B) 75 C) 77 D) 79 E) 81..
So which one would it be?
I'm guessing 77 because it's the sum of all your primes? But can you try to explain why?