Hi,
450x = 120y => 15x = 4y
So, x = (4/15)y. Given that x&y are integers. So, for x to be integer y should be of the form 15k where k is a nonzero integer
for y= 15k, x = 4k
1)(xy)/60 = 15k*4k/60 = k^2(integer)
2)(15x)/(4y) = 1(integer)
3)4x/15y = (4/15)^2(not an integer

Hence, D

Answer is D

we know 450x = 120y ( x & y are non zero integers)

on simplifying above relation we get 15x = 4y

or x = 4y/15 and y = 15x/4

since x and y both are integers 1) y should be a multiple of 15 & 2)x should be a multiple of 4

hence xy/60 is integer & 15x/4y = 1 (is a integer)

I hope this was helpful

1) y should be a multiple of 15 & 2)x should be a multiple of 4

hence xy/60 is integer

OA is D.Thanks. I missed this part.

450x = 120y means 15x = 4y
taking LCM of 15 and 4 we have 60.

thus 15*4 = 4*15 xy/60 = true

also, y/x= 15/4. true

thus D it is.