Question

Consider the net of a triangular prism where each unit on the coordinate plane represents five feet. If a can of spray paint covers 25 square feet, how many cans of spray paint are needed to paint the outside of the prism blue? A) 5 cans B) 7 cans C) 10 cans D)14 cans

Answer 1

B) 7 cans

Explanation:

First task is to determine how many square units we have.

With the rectangle spanning 2 units on the X-axis and 3 unites on the Y-axis, we know that it has an area of 6 square units.

The two triangle shapes sum up to one unit total, since a triangle's area is (base * height) / 2. Both have a base of 1 unit, and a height of 1 unit... so (1 * 1) / 2 = 1/2 for each triangle. Together, they occupy 1 unit.

So, total is 7 square units. Let's imagine it as a 7-unit by 1-unit rectangle, it will be easier to calculate. Each unit is 5 feet. So, this rectangle measures 35 (7 * 5) feet long, by 5 (1 * 5) feet wide... for a total of 175 (35 * 5) sq feet.

Since a can of paint can cover 25 sq feet, he'll need 7 cans (175 / 25).