Bài 1:
a: 4,3m=43dm
\(S=\dfrac{12\cdot43}{2}=6\cdot43=258\left(dm^2\right)\)
b: \(S=\dfrac{0.6\cdot1.5}{2}=\dfrac{0.9}{2}=0.45\left(m^2\right)\)
Bài 2:
a: \(C=\dfrac{4}{5}\cdot2\cdot3.14=5.024\left(dm\right)\)
\(S=\left(\dfrac{4}{5}\right)^2\cdot3.14=2.0096\left(dm^2\right)\)
b: \(C=1.2\cdot3.14=3.768\left(m\right)\)
\(S=0.6^2\cdot3.14=1.1304\left(m^2\right)\)

4 và 5