一道PREP的数学题

Bourne_NY

    

If
500 is the multiple of 100 that is close to x and 400 is the multiple
of 100 that is close to y, which multiple of 100 is closest to x+y?

    

(1)
x<500

    

(2)
y<400

不懂题目什么意思，哪位能给解释一下？