You have 5 brownies for the length plus a 4 cm border around each edge of the brownies.
Ok, we know each side of the brownie is 8 cm so we have 8 x 5 = 40cm. We also know there is a 4 cm border on each side, which we have two sides for the length so 40 cm + 4 + 4 = 48cm
The length is 48 cm.
