how to measure rectagles with timetables

L.I to measure rectangles by using unit squaers and time tables
This week for math I was learning how to measure are rectangle with time tables and what we only need is are paper that  has rectangles and are pencil that is all what we need and we had to measure it and like if a measure the length it is 4 for me and the bottom of the rectangle is 7 so 4 x7 = ?
So the answer of 4x7=28 that is are easy way to find out and know you timetables