18. A ructangular brich has a ienget of 5 centimetors, width of 9 centimuters and a haight of 20 centimeters. What is the surface ares of that brick?

To find the surface area of a rectangular brick, you'll want to use the formula: Surface Area = 2(lw + lh + wh), where l is the length, w is the width, and h is the height. So here, your dimensions are length = 5 cm, width = 9 cm, and height = 20 cm. Plugging in the values: Surface Area = 2(5 * 9 + 5 * 20 + 9 * 20) = 2(45 + 100 + 180) = 2(325) = 650 square centimeters. Voilà! Your brick has a surface area of 650 cm²! When you're calculating surface areas, it's easy to make mistakes—like accidentally flipping length and width or miscalculating dimensions. A common pitfall is forgetting to double the area of each side. Always double-check your work, and maybe use a calculator to avoid simple arithmetic errors!