The shape of sail is triangle
The shape of the boat is trapezoid
Fabric needed for sail = fabric needed for boat
which mean ;
the area of triangle = the area of trapezoid
the area of triangle = 0.5 * base * height
base = bottom sail = 10 and height = 10
∴ the area of triangle = 0.5 * 10 * 10 = 50 ⇒⇒⇒⇒⇒(1)
the area of trapezoid = 0.5 * (b₁ +b₂) * h
b₁ = long base
b₂ = short base = 10 cm.
h = height = 4 cm.
∴ the area of trapezoid = 0.5 (b₁ + 10 ) * 4 ⇒⇒⇒⇒ (2)
Equating (1) and (2)
∴ 0.5 (b₁ + 10 ) * 4 = 50
b₁ + 10 = 25
b₁ = 15
∴ The length of the long base of the trapezoid = 15 cm.
The correct answer is option (C)
