Let’s find the length and width of the enclosing rectangle:
Length=1+5+1=7. Width=5. Area=7×5=35cm².
The area of each narrow rectangle is 5cm² and there are 4 of them, making 20cm².
So the shaded area=35-20=15cm².
Another way to solve it is to find the dimensions of the shaded area. Width=5-1-1=3cm. Length=5cm. So area=3×5=15cm².