Let x cm be the height of triangle. If the base of the triangle is 5 times the height, then the base is 5x cm.
Find the area of triangle using formula
[tex]A=\dfrac{1}{2}\cdot \text{base}\cdot \text{height}.[/tex]
Thus,
[tex]1440=\dfrac{1}{2}\cdot 5x\cdot x=\dfrac{5x^2}{2}.[/tex]
Solve this equation:
[tex]5x^2=1440\cdot 2,\\ \\5x^2=2880,\\ \\x^2=2880:5=576,\\ \\x=24\ cm.[/tex]
Answer: correct choice is B.
