An exam will have 20 questions worth a total of 100 points. There will be true-false questions worth 3 points each and short answer worth 11
points each. The students want to know how many of each type there
will be on the test. The teacher won't tell. How many short answer
questions are there?

  6 +2√3 ft²

Step-by-step explanation:

Given a triangular pyramid with ...

Find

Solution

Since corresponding edges are the same length, the area of each of the three faces is (6 ft²)/3 = 2 ft². This can be computed by ...

  A = (1/2)s²·sin(α)

where s is the lateral edge length and α is the angle at the apex formed by the two edges that meet there. Filling in the given values, we find ...

  2 ft² = (1/2)(2 ft)²·sin(α)

  1 = sin(α)   ⇒   α = 90°

That is, each face of the pyramid is an isosceles right triangle with legs of length 2 ft. The hypotenuse of that triangle, the base edge of the pyramid, is then 2√2 ft.

So, the base is an equilateral triangle with edge lengths 2√2 ft. Its area can be computed from ...

  A = (√3)/4·s²

where s is the edge length of the equilateral triangle. That is, the base area is ...

  A = (√3)/4·(2√2)² = 2√3 . . . . square feet

So, the total surface area of the pyramid is ...

  (6 +2√3) ft² ≈ 9.4641 ft² . . . . . total surface area