If 500 is the multiple of 100 that is closest to x and 400 is the multiple of 100 that is closest to y, which multiple of 100 is closest to x+y?
(1) x < 500
(2) y < 400
okay, so off the bat we can tell that 450<x<550 and 350<y<450 because in order for x and y to be closest to 500 and 400 respectively, they need to be within those ranges. 450 is equally as close to 400 and 500, and 434 is closer to 400 than 500, for example.
so 800<x+y<1000
now this doesn't solve our answer, but it's a start. Let's correct our formulas for each part.
(1)
450<x<500
800<x+y<950
this tells us it's either 800 or 900, but not which one.
(2)
350<y<400
800<x+y<950
same as (1)
together
800<x+y<900.
it could be either 800 or 900 still, so I'd go with E.
