Dmitri wants to cover the top and sides of the box shown with glass tiles that are 5mm square. how many tiles does he need? ( the length is 15cm, the width is 20cm and the height is 9cm).

The Surface Area = lw + 2lh + 2wh;
The Surface Area = 15*20 + 2*15*9 + 2*20*9;
The Surface Area = 300 + 270 + 360;
The Surface Area = 570 + 360;
The Surface Area = 930cm^2;
The surface of glass tile is 5 × 5 = 25 cm^2;
Then, 930 ÷ 25 = 37.2;
He need 38 tiles to cover the top and sides of the box shown.