a)
[tex]10mm = 1cm \\ \\ 1 \times 2 = 2 {cm}^{2} [/tex]
b)
[tex]12dm = 1.2m \\ \\ \frac{2.5 \times 1.2}{2} = \frac{3}{2} = 1.5 {m}^{2} [/tex]
c)
[tex]0.5m = 5dm \\ 300mm = 30cm = 3dm \\ \\ \frac{(5 + 3) \times 3}{2} = \frac{8 \times 3}{2} = 4 \times 3 = 12 {dm}^{2} [/tex]
d)
[tex] \frac{(4 + 4) \times (3 + 3)}{2} = \frac{8 \times 6}{2} = 4 \times 6 = 24 {cm}^{2} [/tex]
