Pritishd
If the sum of two positive integers is 592 and their HCF (GCD or greatest common divisor) is 37, then how many such pairs exist?
A. 8
B. 7
C. 4
D. 16
E. 15
We are told that the greatest common factor of two integers is 37. So, these integers are \(37x\) and \(37y\), for some positive integers \(x\) and \(y\). Notice that \(x\) and \(y\) must not share any common factor but 1, because if they do then GCF of \(37x\) and \(37y\) will be more that 37.
Next, we know that \(37x+37y=592\) --> \(x+y=16\) --> since \(x\) and \(y\) don't share any common factor but 1 then (x, y) can be only (1, 15), (3, 13), (5, 11) and (7, 9) (all other pairs (2, 14), (4, 12), (6, 10), (8, 8) do share common factor greater than 1). So, there are only four pairs of such numbers possible: 37*1=37 and 37*15=555; 37*3=111 and 37*13=481; 37*5=185 and 37*11=407 AND 37*7=259 and 37*9=333.
Answer: C.
I have a very basic question that should the question not ask for unique pairs instead of just pairs? I am talking about (1, 15) and (15, 1). I understand that they are both the same and yield the same result, but from a value stand point we are assigning two different values to \(x\) and \(y\)