Rectangular prism:  SA = 2lw+2lh+2wh

Triangular prism:  SA = wh + lw + lh + ls

To estimate the surface area, first round each decimal number to a whole number.

length = 7 m
width = 6 m
                                       height = 3 m

Now use the formula:

SA = 2lw+2lh+2wh
SA = 2(7)(6) + 2(7)(3) + 2(6)(3)
SA = 84 + 42 + 36
162 m²

To estimate the surface area, first round each decimal number to a whole number.

(Dimensions are in cm)    length = 11 cm
                                         width = 5 cm
                                         height = 7 cm
                                         side = 8 cm

Now use the formula:

 SA = wh + lw + lh + ls
SA = 5(7) + 11(5) + 11(7) + 11(8)
SA = 35 + 55 + 77 + 88
255 cm²