Adding whole hundreds (3 addends)

Students can add left to right, or look for two hundreds that combine to a round number like 1,000 first, then add the third hundred — mirroring the make-a-ten strategy at a larger scale.

Sums most commonly fall between 300 and 900 when keeping all three addends within the hundreds of 100-400; problems may extend to sums of 1,000 as enrichment.

Estimating totals in grocery shopping, budgeting, or measuring distances in hundreds of feet all involve the same mental addition students practice with these problems.