What is the solution to the problem expressed to the correct number of significant figures? 2.13 + 1 = ?

2.13 + 1 = 3

When adding values, you must round your answer to the same "place" as the measurement with its last significant figure furthest to the left.

2.13

+1

3.13

The "1" has its last significant figure furthest to the left, so you round off the number to the "units" place. That's the last column that the measurements share.

3.13 → 3 (rounded to the "units" place)

∴ 2.13 + 1 = 3