Answer given was 49 451. Can you please explain how?

Yes, you are correct. But can you please explain why you take those numbers instead of 70,499 and 19 950?

A is rounded to nearest *thousand.
So all these number from 69500 to 70499 will results in 70 000.
Example:
69500
69501
69502
69503
.
.
.
70497
70498
70499
70500 - cannot. Cause round off to thousand is 71000 :)

B is rounded to nearest *hundred
So all these number from 19950 to 20049 will results in 20000.
Example :
19950
19951
19952
.
.
.
20047
20048
20049
20050 cannot too, rounded to nearest hundred is 20100 :)

Therefore, to get SMALLEST possible A-B. You must choose Smallest A number, ie 69500
And biggest B number, ie 20049.

So A-B will be smallest.

Thanks. The question is so tricky..

Yes. Another word is the 2 number closest to each other. - for smallest.

For biggest possible , choose 2 number furthest to each other.

Hope it helps.

I got it now... thanks thanks...