If each side of an equilateral triangle is $37\sqrt{3}$ cm, then its altitude (in cm) is equal to:
37.5
18.5
60.5
55.5
Correct answer: 55.5
Solution
In an equilateral triangle, altitude = $\frac{\sqrt{3}}{2}a$. Substituting $a=37\sqrt{3}$ gives altitude $=\frac{\sqrt{3}}{2}\times 37\sqrt{3}=\frac{37\times 3}{2}=55.5$ cm.