Question

An oak tree that is 220 years old produced acorns at two different rates. Until it reached maturity, it produced an average of 900 acorns a year. However, once the tree reached maturity, it produced an average of 2200 acorns a year. One particular tree, Angel Oak, has produced about 289,000 acorns in its lifetime. At what age did it reach maturity?

A) 188
B) 150
C) 138
D) 148

Answer 1

The answer is B: 150

Let a be the age at which the tree reaches maturity

289000 = 900a + 2200(220-a)
289000 = 900a + 484000 - 2200a
289000 - 484000 = -1300a
a = -19500 / -1300
a = 150