The area of a triangle is equal to ½ base x height:

a = ½bh
a = ½ x 1 x 1 = \( \frac{1}{2} \) = \(\frac{1}{2}\)

The surface area of a cube is (2 x length x width) + (2 x width x height) + (2 x length x height):

sa = 2lw + 2wh + 2lh
sa = (2 x 4 x 2) + (2 x 2 x 9) + (2 x 4 x 9)
sa = (16) + (36) + (72)
sa = 124

For parallel lines with a transversal, the following relationships apply:

• angles in the same position on different parallel lines equal each other (a° = w°, b° = x°, c° = z°, d° = y°)
• alternate interior angles are equal (a° = z°, b° = y°, c° = w°, d° = x°)
• all acute angles (a° = c° = w° = z°) and all obtuse angles (b° = d° = x° = y°) equal each other
• same-side interior angles are supplementary and add up to 180° (e.g. a° + d° = 180°, d° + c° = 180°)

Applying these relationships starting with d° = 142, the value of c° is 38.

The surface area of a cylinder is 2πr² + 2πrh:

sa = 2πr² + 2πrh
sa = 2π(8²) + 2π(8 x 7)
sa = 2π(64) + 2π(56)
sa = (2 x 64)π + (2 x 56)π
sa = 128π + 112π
sa = 240π

The formula for circumference is circle diameter x π:

c = πd
c = 8π