High School

What is the rate of decay, [tex] r [/tex] (expressed as a decimal), for data best modeled by the exponential function [tex] y=63.4(0.92)^t [/tex]?

A. [tex] r=36.6 [/tex]
B. [tex] r=0.92 [/tex]
C. [tex] r=0.08 [/tex]
D. [tex] r=63.4 [/tex]

Answer :

Certainly! Let's solve this step-by-step:

The given exponential function is [tex]\( y = 63.4(0.92)^x \)[/tex].

In an exponential decay function of the form [tex]\( y = a(b)^x \)[/tex]:

- [tex]\( a \)[/tex] is the initial amount (63.4 in this case).
- [tex]\( b \)[/tex] is the base of the exponential, which tells us how much the quantity decreases as a power of [tex]\( x \)[/tex].

If [tex]\( b \)[/tex] is less than 1, it represents exponential decay, and the rate of decay, [tex]\( r \)[/tex], can be calculated as [tex]\( 1 - b \)[/tex].

Here's how the calculation works:

1. Identify the value of [tex]\( b \)[/tex] in your function. In this function, [tex]\( b = 0.92 \)[/tex].

2. Calculate the rate of decay [tex]\( r \)[/tex] using the formula:

[tex]\[
r = 1 - b
\][/tex]

Plug in the value of [tex]\( b \)[/tex]:

[tex]\[
r = 1 - 0.92
\][/tex]

3. Perform the subtraction:

[tex]\[
r = 0.08
\][/tex]

Therefore, the rate of decay expressed as a decimal is [tex]\( r = 0.08 \)[/tex]. This means each unit of time, the quantity decreases by 8%.

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