26.45 + 2.55 = 29 . . . but with correct sig figs . . . the answer is . . . 29.00 . . . i.e. [4] sig figs
. . . why? . . . because even though 26.45 has [4] sig figs & 2.55 has [3] sig figs, the number of sig figs to the right of the decimal are the critical sig figs . . . and there are [2] sig figs to the right of the decimal, so the answer/result can also beas precise as having [2] sig figs to the right of the decimal as well.