A tree casts a shadow of 28 feet. At the same time, a biologist who is 7 feet tall casts a shadow of 2 feet. How tall is the tree? 8 feet 14 feet 78 feet 98 feet

Let the height of the tree = X

Now set up a ratio the height of the man over the height of his shadow = the height of the tree over the length of its shadow:

7 ft / 2 ft = X / 28 ft

Now cross multiply the fractions:

7 * 28 / 2 * X = 196 / 2X

X = 196 / 2

X = 98

The tree is 98 feet tall