What do you round 150 to?

It depends on what you are rounding off to.

If you are round it off to the nearest ten, you must look at the unit number.

If you are rounding off to the nearest hundred, you must look at the ten number.

In this case I think they are asking to round to the nearest hundred. Now we must look at the ten number, which is the number after the 'hundred' number.

The ten number is '5' and the hundred number is '1'. If the ten number is 5 or above, it changes to 0 and it makes the hundred number one higher.

So because the ten number is 5, it changes to 0 and it makes the hundred number one higher, to become 2.

The number is now 200.