Answer:
30 ft
Step-by-step explanation:
We can use the given information to set up a ratio...
[tex]\frac{Mark's\ height}{Mark's\ shadow}=\frac{Tree's\ height}{Tree's\ shadow}[/tex]
[tex]\frac{6\ ft}{4\ ft}=\frac{x}{20\ ft}[/tex]
We can solve this ratio using cross multiplication (multiply the numerator of the first fraction by the denominator of the second and the numerator of the second fraction by the denominator of the first):
120 = 4x
Divide both sides by 4
x=30 ft
