Wyatt put the $450 she earned from her summer job into an account and will use it to pay for school expenses. She withdraws 10% of the remaining balance each month to pay for part of her living expenses. Which of the following functions models the balance, B, of Wyatt's money (in dollars) t months after she started school?Choose 1 answer:(A) B(t)=450⋅(1.1)t(B) B(t)=450⋅(0.9)t(C) B(t)=450+1.1t(D) B(t)=450−0.9t
Q. Wyatt put the $450 she earned from her summer job into an account and will use it to pay for school expenses. She withdraws 10% of the remaining balance each month to pay for part of her living expenses. Which of the following functions models the balance, B, of Wyatt's money (in dollars) t months after she started school?Choose 1 answer:(A) B(t)=450⋅(1.1)t(B) B(t)=450⋅(0.9)t(C) B(t)=450+1.1t(D) B(t)=450−0.9t
Problem Understanding: Understand the problem.Wyatt withdraws 10% of the remaining balance each month. This means that each month, she has 90% of the previous month's balance left.
Mathematical Model: Translate the situation into a mathematical model.Since Wyatt withdraws 10% each month, the balance is multiplied by 0.9 each month. This is a geometric sequence where each term is 0.9 times the previous term, starting with 450.
Identifying the Function: Identify the correct function.The function that models a quantity that decreases by a constant percentage over time is an exponential decay function. The general form of such a function is B(t)=B0⋅(1−r)t, where B0 is the initial amount, r is the decay rate, and t is time.
Matching the Situation: Match the situation with the given options.The correct function must have an initial amount of 450 and a decay rate of 10%, which is 0.1. Therefore, the function should be B(t)=450×(1−0.1)t=450×(0.9)t.
Choosing the Answer: Choose the correct answer.The function that matches our model is B(t)=450×(0.9)t, which is option (B).
More problems from Compare linear and exponential growth