Answer:
<em>820</em>
Explanation:
Round to the nearest multiple of 10 (ex. 180, 190, 230, 240)
233 rounds to 230, going down.
189 rounds to to 190, going up.
402 rounds to 400, going down.
230 + 190 + 400 equals <em>820</em>.
The question didn't specify, and the best way to estimate more accurately<em> </em>is by using multiples of 10.