Round, then Estimate the Sum

Eight additions are printed one to a row on this 3rd grade page, each followed by three dashed boxes: one for the first number rounded, one for the second, and one for the two rounded numbers added. The reference band works 23 plus 48 into 20 plus 50 equals 70. The sheet shown runs 12 plus 51, 29 plus 14, 59 plus 19, 31 plus 32, 35 plus 28, 15 plus 36, 38 plus 52 and 63 plus 27, so every estimate stays at or under one hundred.

This is the only face in the family that puts rounding to work, and the three boxes keep the two steps apart so a child cannot add first and round afterwards. Both numbers have to be handled before the addition can start, which is twice the decision of the base page for the same number of rows. Two of the eight estimates happen to land on the exact sum, which is a useful thing to notice and a good question to ask at the end.

One sheet, eight additions, twenty-four boxes. The addends are all two digits and the totals stay inside a hundred, so the final column can be done in the head once the rounding is on the page. Give it after the base and the sort faces, when rounding is quick enough that it does not swamp the estimating it is supposed to serve.