The height of a certain tree varies directly with its age. When it is 15 years old, it is 18 feet tall. How tall will it be when it is 25?

Answer 1

The phrase y varies directly with x means we can model the equation as y = kx, where k is some constant.

Here we have that height varies directly with age. So height = k(age). In addition, we know that at 15 years old, the tree is 18 ft. This means that 18 = k(15). We can then solve for k. Thus, k = 18 /15 = 6 / 5. The final equation we get is that height = (6/5) * age. We can then find the height of the tree at 25 years old by plugging in 25 into the equation.

Answer 2

It depends on the rate of growth. However if the tree keeps the same rate of growth (15 years/ 18 feet) then we can figure out the height of the tree when it is 25 years of age.

18/15 = x / 25

We can find the height of the tree at 25 by multiplying both sides of the equation by 25

25 * (18/15) = x

30 = x