Question from GMATprep software: DS : Numbers

[iamseer]

If 500 is multiple of 100 that is closest to x and 400 is the multiple of 100 closest to y, which multiple of 100 is closest to x+y?
1. x<500
2. y<400

To be very frank I don't quite get what is being said in the question and hence don't understand what is being asked.

Please help with answer explanation.
Many thanks.

[meghash3]

Ans: BOth statements together sufficient, niether individually.

Expln. : It is said 500 is closest to a multiple of 100 - Y and similarly for 400 & x too

stmt 1 & 2 give us that X & Y < 500 and 400 resptly.

now multiple of 100 < 500 is 400 and < 400 is 300.

thus 700 is the multiple of 100, x+y is closest to, thus both together suff.

[iamseer]

thanks for the quick reply meghash3. Your reply lighted the bulb in my head The correct answer is E. (Source: GMATprep)

I felt it but couldn't reason it. But with the help of your post now I have an explanation.

from Q stem:
450<x<550 and
350<y<450

From 1:
x<500. Therefore 450<x<500. No info of y. INSUFFICIENT

From 2:
y<400. Therefore 350<y<400. No info of x. INSUFFICIENT

Combining 1 and 2:

450<x<500 and 350<y<450, therefore
800<x+y<900. We don't know whether x+y is close to 800 or 900 so answer is E.

let me know your thoughts.
Thanks again.

[el_torero]

My answer is E.

Lets looks at the statements:

(1) x < 500

This means 500 is closest to x < 500. Which can either be 499, or 451 (I chose extreme cases as an example). Note that 450 would make the question ambiguous since is 500 closest to 450, or 400? Also note anything less than 450 can't be considered because then our multiple of 100 closest to x would be 400.

Well, y can be anything so (1) is INSUFF.


(2) y < 400

Same logic. Pick 399, 351. Either way, (2) is still INSUFF

Both:
Using those values we chose above, x + y could equal 898, 850, or 802. Which means multiple of 100 could be 900, or 800. INSUFF.

[eaakbari]

thanks for the quick reply meghash3. Your reply lighted the bulb in my head The correct answer is E. (Source: GMATprep)

I felt it but couldn't reason it. But with the help of your post now I have an explanation.

from Q stem:
450<x<550 and
350<y<450

From 1:
x<500. Therefore 450<x<500. No info of y. INSUFFICIENT

From 2:
y<400. Therefore 350<y<400. No info of x. INSUFFICIENT

Combining 1 and 2:

450<x<500 and 350<y<450, therefore
800<x+y<900. We don't know whether x+y is close to 800 or 900 so answer is E.

let me know your thoughts.
Thanks again.

This is the correct way to go about it. Answer is E