Solve the problem.
-Tia is going to stain her triangular concrete patio. The patio is approximately 15 feet by 18 feet by 10 feet. If one can of stain covers $$15 \mathrm { ft } ^ { 2 }$$ how many cans of stain will she need?
A) 66 cans
B) 2 cans
C) 90 cans
D) 5 cans

Question

Quizplus · Accepted Answer

To find the number of cans needed, first calculate the area of the triangular patio using Heron's formula. The semi-perimeter (s) is $\frac{15 + 18 + 10}{2} = 21.5$ feet. The area (A) is $\sqrt{s(s - a)(s - b)(s - c)} = \sqrt{21.5(21.5 - 15)(21.5 - 18)(21.5 - 10)} \approx 72 \mathrm { ft } ^ { 2 }$. Since one can covers 15 square feet, Tia will need $\frac{72}{15} = 4.8$ cans. Since she can't buy a fraction of a can, she'll need to round up to 5 cans.

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