Question

Food bank usage in Britain has grown dramatically over the past decade. The number of users, in thousands, of the largest food bank in year t is estimated to be N(t) = 1.3e0.81t , where t is the number of years since 2006.25

(a) What does the 1.3 represent in this context? Give units.


(b) What is the continuous growth rate of users per year?


(c) What is the annual percent growth rate of users per year?


(d) Using only your answer for part (c), decide if the doubling time is more or less than 1 year.

Answer 1

A) 1.3 represents the number of foodbank users in thousands in the year 2006

B) 0.81 per year

C) 124.79%

D) the doubling rate is less than a year.

Explanation:

A) We are given N(t) = 1.3e^(0.81t) where t in thousands the number of years since 2006. N(t) is in thousands

Thus, in 2006,t = 0.

So, N(0) = 1.3e^(0.81 × 0)

N(0) = 1.3

Thus,1.3 represents the number of foodbank users in thousands in the year 2006

B) From the question, we see that the continuous growth rate is 0.81t.

This is 0.81 per year

C) The exponent of the growth rate is e^(0.81t).

Thus gives; 2.2479^(t)

This means the annual growth factor for each year is 2.2479.

Thus,annual percent growth rate is;

(2.2479 - 1) × 100% = 124.79%

D) From C above we saw that the annual percent growth rate is more than 100%. This means that it takes less than a year for the number of users to be doubled.. Thus, the doubling rate is less than a year.