The 9 is in the thousands place.
Look one digit to the right, in the hundreds place.
If that digit is 5 or greater, then add 1 to the 9.
If that digit is 4 or less, then leave the 9 alone.
Replace everything to the right of the 9 with 0s.
0 in the hundreds place.
0 is 4 or less, so leave the 9 alone.
Answer: 49,000
If the problem had been to round 49,552 to the nearest thousand, then the 5 in the hundreds place would have made the 9 go up by 1 and the answer would have been 50,000.