You can use similar triangles to determine the height of the tree. The relationship between the height of the man and the length of his shadow can be set equal to the relationship between the height of the tree and the length of its shadow.
Let \( h \) be the height of the tree. According to the given information:
\[ \frac{6 \text{ ft}}{4 \text{ ft}} = \frac{h}{60 \text{ ft}} \]
Now, cross-multiply to solve for \( h \):
\[ 6 \text{ ft} \times 60 \text{ ft} = 4 \text{ ft} \times h \]
\[ 360 = 4h \]
Now divide both sides by 4:
\[ h = \frac{360}{4} = 90 \text{ ft} \]
So, the height of the tree is 90 feet.