2. Вычислите удобным способом.

a) 0.4 + 0.06 + 0.6 + 0.04 = (0.4 + 0.6) + (0.06 + 0.04) = 1.0 + 0.1 = 1.1. b) 3.9 + 1.3 − 0.3 + 2.1 = (3.9 − 0.3) + (1.3 + 2.1) = 3.6 + 3.4 = 7.0. c) 0.36 + 0.04 + 1.51 − 0.51 = (0.36 + 0.04) + (1.51 − 0.51) = 0.4 + 1.0 = 1.4. d) 2.07 + 5.45 + 4.55 + 3.03 = (2.07 + 3.03) + (5.45 + 4.55) = 5.1 + 10.0 = 15.1.