求助prep数学题目！

各位高人，请帮忙！万分感谢！

1、is the hundredths digit of the decimal d greater tahn 5?

(1) the tenths digit of 10d is 7;

(2) the thousandth digit of d/10 is 7;

Ans: D

(2) if 500 is the multiple of 100 that's 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;

Ans: E

拜托请指点！

你好！我第二题也不懂题目什么意思。。。

请赐教，为何说：x的范围在(450,500),y本身的范围根据题干是(350,450) ？？

谢谢！