Answer:
18. 2,047.5 yd³
19. 3204 in.²
Explanation:
18. Volume of triangular prism = triangular base area × height of prism
Height of prism = 21 yd
Triangular base area = ½*b*h
b = 15 yd
h = √(15² - 7.5²) = √168.75 ≈ 13 yd
Triangular base area = ½*15*13 = 97.5 yd²
Plug in the values into the formula of the volume of prism
Volume of prism = 97.5 × 21
= 2,047.5 yd³
19. Surface area = 2πrh + 2πr²
Where,
r = 15 in.
h = 19 in.
Plug in the values
Surface area = 2*π*15*19 + 2*π*15²
Surface area = 3204.42 ≈ 3204 in.² (nearest whole number)