Problem:
A barn with a flat roof is rectangular in shape, 10 yd. wide, 13 yd. long and 5 yd. high. It is to be painted inside and outside, and on the ceiling, but not on the roof or floor. The total number of sq. yd. to be painted is:
Answer Choices:
A. 360
B. 460
C. 490
D. 590
E. 720
Solution:
S=1(13⋅10)+2[2(13⋅5)+2(10⋅5)]=1(130)+2[2(65)+2(50)]=130+2[130+100]=130+2[230]=130+460=590