For more examples about calculating surface area of a cone, pyramid, or sphere see pp. 69 to 71 of Mathematics 10.

 

In the lesson and textbook examples, you saw how to use the surface area formula to determine the surface area of newly introduced objects whose dimensions were known.

As shown using the area problems in the Warm Up, an unknown dimension can also be determined when the surface area and the other dimensions of an object are given. 

 

Example 5

In ancient times, the Great Pyramid of Giza was constructed. It has a surface area of 138 977.28 m2 and a square base of length 230.4 m. Determine the slant height of the pyramid, expressed to the nearest tenth of a metre.

 


Step 1: Substitute the given measurements into the formula for the surface area of a pyramid.

Step 2: Solve for the missing dimension, s = slant height.

Step 3: State your solution in sentence form.

The slant height of the Giza Pyramid is 186.4 m.

 

For an example about determining a missing dimension of a sphere see p. 71 of Mathematics 10.