Natural Logarithms

Question

Round answer to two decimal places. An animal grows according to the formula L(t) = 20 ln(2 + 5t), where L is the weight in pounds and t is the age in years. The age, in years, of a 40 pound animal is: (a) 1.08 (b) 1.48 (c) 105.97 (d) 106.17 (e) none of these

Answer 1

40=20ln(2+5t)

2=ln(2+5t)

e²=7.389056=2+5t

5.389056=5t

t=1.077, i.e. the answer is 1.08