High School

You win a prize and are offered two choices:

**Choice A:** [tex] \$0.10 [/tex] on January 1, [tex] \$0.20 [/tex] on January 2, [tex] \$0.40 [/tex] on January 3, [tex] \$0.80 [/tex] on January 4, doubling the amount each day.

**Choice B:** [tex] \$5.00 [/tex] on the first day, [tex] \$10.00 [/tex] on the second day, [tex] \$15.00 [/tex] on the third day, getting [tex] \$5.00 [/tex] more each day.

Which choice can be defined using an exponential function? What is the function?

A. Choice B, [tex] A_t = 5.00 + 5.00t [/tex]

B. Choice A, [tex] A_t = (0.10)^{t-1} [/tex]

C. Choice A, [tex] A_t = 0.10(2)^{t-1} [/tex]

D. Choice B, [tex] A_t = 5.00 + 5.00(t-1) [/tex]

Answer :

To determine which choice can be defined using an exponential function, let's examine both options provided:

Choice A: Starts with [tex]$0.10 on January 1, and the amount doubles each day. So, on January 2 it's $[/tex]0.20, on January 3 it's [tex]$0.40, and so on. The amounts are 0.10, 0.20, 0.40, 0.80, etc.

This represents exponential growth because the amount is multiplied by 2 each day. We can define an exponential function for this pattern as \( A_t = 0.10 \times 2^{t-1} \), where \( t \) is the day number.

Choice B: Begins with $[/tex]5.00 on the first day, then increases by [tex]$5.00 each subsequent day. So, on the first day, you get $[/tex]5.00, on the second day [tex]$10.00, on the third day $[/tex]15.00, and so forth. The amounts are 5.00, 10.00, 15.00, 20.00, etc.

This pattern shows a linear growth because the amount increases by a fixed value each day. The function for this linear pattern can be expressed as [tex]\( A_t = 5.00 + 5.00(t-1) \)[/tex], where [tex]\( t \)[/tex] is the day number.

Since an exponential function is characterized by a constant multiplicative rate of change (doubling, in this case), Choice A can be defined using an exponential function. The function for Choice A is:

[tex]\[ A_t = 0.10 \times 2^{t-1} \][/tex]

This means on any day [tex]\( t \)[/tex], the amount you receive is 0.10 multiplied by 2 raised to the power of [tex]\( t-1 \)[/tex].