Step 1
State the formula that can be used to simplify the problem

Step 2
Find the area to be covered
![=length* width=\text{ 20cm }*28\operatorname{cm}=560cm^2]()
Step 3
Find the area of 1 tile
![\begin{gathered} =length* width=4\operatorname{cm}*2\operatorname{cm} \\ =8\operatorname{cm}^2 \end{gathered}]()
Step 4
Find the number of tiles required
![=\text{ }\frac{560\operatorname{cm}}{8\operatorname{cm}^2}]()

Hence 70 4cm by 2cm tiles will be needed to cover an area that measures 20cm by 28cm