Explain how you would round the numbers 33 and 89 to estimate their sum

Round each number to the nearest 10.
33 rounds to 30 and 89 rounds to 90, thus in your head it's easier to mentally add 30 + 90 for purposes of estimation.

30 and 90... If the last number is 4 or lower than you round down... If the last number is 5 or higher than you round up... So the 3 in 33 is below four so you round down to 30 and the 9 in 89 is hight than 5 so therefore you round up to 90