Estimate the sum in two different ways:
A) By rounding off to the highest place value (hundreds):
368 = 400 (3 hundreds is the highest place value)
231 = 200 (2 hundreds is the highest place value)
400 + 200 = 600
B) By rounding off to the second highest place value (tens):
368 = 370
231 = 230
370 + 230 = 600