两道prep数学题

1、If 500 is the mulitple 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.

2、A hiker walking at a constant rate of 4 miles per hour is passed by a cyclist traveling in the same direction along the same path at a constant rate of 20 miles per hour. The cyclist stops to wait for the hiker 5 minutes after passing her, while the hiker continues to walk at her constant rate. How many minutes must be the cyclist wait until the hiker catches up.

这两道题题目都没有看懂，大家帮帮忙哦，O(∩_∩)O

怎么没人帮我回答呢？？

大家帮帮忙哦，题目都没看懂呢。

第二题应该是 20/60 * 5= 5/3  then  5/3 / 4/60= 25  then  25-5=20

I have no chinese type this moment...sorry

do you understand?

还是不太明白呢。我想知道题目的意思。。。。。

我觉得第一题原题条件是 ： 451《x《550 和 351《y《450  

（1）和（2） 结合 可以推出 802《x+y《 900   这个值可以是 800（比如803） 或者900 （比如890）    不知道这样对不对