Composite figure

Question

Determine the total perimeter AND area of the following crayon (composite figure) to  (to one decimal place):

 

the tip=14cm

 

the body=35cm

 

the bottom with a radius of = 5cm

Answer 1

For a 2-D composite figure:

 

Treat the tip as a triangle with height(h) 14cm and base(b) 10cm. Treat the body as a rectangle with length(l) 35cm and width(w) 10cm. We got the base of the triangle and width of the rectangle by doubling the radius(r). Insert these values into the following formulas:

 

Area of triangle: b x h/2

Area of rectangle: l x w

Total area: area of rectangle + area of                         triangle

 

Total perimeter : 2l + w + 2H, where H is any of the 2 sides of the triangle other than its base.

To find out the value of H, use the pythagorean theorem:

r² + h² = H²