For triangles, area is 1/2 base times height 8. Base 15 1/4 and height 18. Base and height can be flipped around to make the math easier, so 1/2(18)(15 1/4) = 9(15 1/4) = 9(61/4) = 549/4= 137 1/4 sq inches
9. Base 13 and height 11. Area = (1/2)(13)(11)= (13/2)(11) = 143/2 = 71 1/2 sq inches
10. Same thing again. Base = 30, height = 20, so area = (1/2)(30)(20) = 15(20) = 300 square km.
11. Base = 8, height = 5, so (1/2)(8)(5)= 4(5)= 20 square feet.
12. Base = 5, height = 3, so area = (1/2)(5)(3)= (5/2)(3)= 15/2; for 200 tiles we would take (15/2)(200)= 15(100) = 1500 square cm
13. Monica forgot to multiply base and height by 1/2.
