Question

78 mm + 40 cm em metros​

Answer 1

78 mm + 40 cm

7,8 cm + 40 cm

47,8 cm =====> 0,478m

Answer 2

$mm = 10 {}^{ - 3} m \\ \\ cm = 10 {}^{ - 2} m \\ \\ 78 \times 10 {}^{ - 3} m + 40 \times 10 {}^{ - 2} \\ \\ 0.078m + 0.4m \\ \\ 0.478m$