38. Siobhan rounds 99,498 to the nearest thousand and gets 100,000. What mistake did Siobhan make?

Siobhan made a mistake in rounding. When rounding to the nearest thousand, you should look at the hundreds digit (the digit in the thousands place) to decide whether to round up or down. In the number 99,498, the hundreds digit is 4. Since 4 is less than 5, you should round down. Therefore, rounding 99,498 to the nearest thousand should result in 99,000, not 100,000. Siobhan incorrectly rounded up instead of rounding down, leading to the mistake. The correct rounded value is 99,000.