To round a number to the nearest 10, we look at the digit in the ones place. If the digit is 5 or greater, we round up by adding 10 to the number. If the digit is less than 5, we round down by simply keeping the tens digit and discarding the ones digit. In this case, the digit in the ones place is 8 which is greater than 5, so we round up. Adding 10 to 238 gives us 248, which is the rounded number to the nearest 10.