求助一道DS

hbjat1989

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
答案是E
我的困惑是~~看不懂题

sdcar2010

multiple of 100: 100, 200, 300, 400, 500, 600, . . .

Among the above candidates, 500 is the closest to x and 400 is the closest to y. Do you know which of the above numbers is closest to x+y?

Premise:  450<x<550 and 350<y<450

condition 1) 450<x<500, 800<x+y<950.  The multiple of 100 could be 800, 900,
condition 2) 350<y<400, 800<x+y<950.  The multiple of 100 could be 800, 900
conditions 1) and 2) 450<x<500, 350<y<400, 800<x+y<900. The multiple of 100 could be 800, 900.


EEEEEEEEEEEEEE