Find the area of a rectangle with length 8 and width 5.

Step-by-step solution

1. 1

   Use the definition of rectangle area. Area counts how many unit squares fit inside the shape. A rectangle of length $8$ holds $8$ unit squares per row, and a width of $5$ stacks $5$ such rows, so the area is a product: $A=\ell\times w$.

2. 2

   Substitute the given dimensions. $A=8\times 5$.

3. 3

   Multiply. $A=40$ square units. The units are squared because two lengths were multiplied.

4. 4

   Distinguish area from perimeter. The perimeter here would be $2(8+5)=26$ units, a different quantity entirely; area fills the inside while perimeter measures the boundary.

5. 5

   Check by counting rows. Five rows of eight squares give $8+8+8+8+8=40$ squares, matching the multiplication.