You can calculate 3444 times 670 without rounding or you can estimate it WITH rounding. But you cannot estimate it without rounding.
670 is ten times bigger than 67.
8 times with a remainder of 70
230 + 670 = 900
6 times remainder 70
9 with remainder 40.
670 rounded to the nearest hundred is 700. 670 rounded to the nearest hundred is 1000.
700
670 is ten times bigger than 67.
670 is 6.7 times larger than 100.
3350
935
67 times exactly !
If you're adding those, you can see clearly that the actual answer is 2985 but if you have to, estimate 2300 + 670 = 2970
671.641791 times
8 times with a remainder of 70
230 + 670 = 900
6 times remainder 70