A stock broker is evaluating the value of a certain share each week. The function that describes the value of the share, [tex]\( v \)[/tex], in dollars, after [tex]\( n \)[/tex] weeks is given below, where [tex]\( b \)[/tex] is an unknown positive base.

[tex]\[ v(n) = 14 \cdot b^n \][/tex]

Select the correct statement:

A. If [tex]\( b = 1.08 \)[/tex], the weekly percent growth rate of the share's value is 8%.

B. If [tex]\( b = 1.06 \)[/tex], the weekly percent growth rate of the share's value is 6%.

C. If [tex]\( b = 0.84 \)[/tex], the weekly percent growth rate of the share's value is -16%.

D. If [tex]\( b = 0.77 \)[/tex], the weekly percent growth rate of the share's value is -23%.



Answer :

Let's thoroughly evaluate the percentage growth rates for each base value provided, step-by-step.

### Basic Understanding:
The weekly percent growth rate can be determined using the formula:
[tex]\[ \text{Growth Rate (\%)} = (b - 1) \times 100 \][/tex]

where [tex]\( b \)[/tex] is the given base value.

### Calculate Growth Rates for Each Base Value:

1. For [tex]\( b = 1.8 \)[/tex]:
[tex]\[ \text{Growth Rate} = (1.8 - 1) \times 100 = 0.8 \times 100 = 80\% \][/tex]
The weekly percent growth rate is [tex]\( 80\% \)[/tex].

2. For [tex]\( b = 106 \)[/tex]:
[tex]\[ \text{Growth Rate} = (106 - 1) \times 100 = 105 \times 100 = 10500\% \][/tex]
The weekly percent growth rate is [tex]\( 10500\% \)[/tex].

3. For [tex]\( b = 0.84 \)[/tex]:
[tex]\[ \text{Growth Rate} = (0.84 - 1) \times 100 = -0.16 \times 100 = -16\% \][/tex]
The weekly percent growth rate is [tex]\( -16\% \)[/tex].

4. For [tex]\( b = 0.77 \)[/tex]:
[tex]\[ \text{Growth Rate} = (0.77 - 1) \times 100 = -0.23 \times 100 = -23\% \][/tex]
The weekly percent growth rate is [tex]\( -23\% \)[/tex].

### Check Statements Against Calculations:

- Statement A: If [tex]\( b = 1.8 \)[/tex], the weekly percent growth rate of the share's value is [tex]\( 8\% \)[/tex].
- From our calculation, for [tex]\( b = 1.8 \)[/tex], the growth rate is [tex]\( 80\% \)[/tex]. This does not match the statement.

- Statement B: If [tex]\( b = 106 \)[/tex], the weekly percent growth rate of the share's value is [tex]\( 6\% \)[/tex].
- From our calculation, for [tex]\( b = 106 \)[/tex], the growth rate is [tex]\( 10500\% \)[/tex]. This does not match the statement.

- Statement C: If [tex]\( b = 0.84 \)[/tex], the weekly percent growth rate of the share's value is [tex]\( 84\% \)[/tex].
- From our calculation, for [tex]\( b = 0.84 \)[/tex], the growth rate is [tex]\( -16\% \)[/tex]. This does not match the statement.

- Statement D: If [tex]\( b = 0.77 \)[/tex], the weekly percent growth rate of the share's value is [tex]\( 23\% \)[/tex].
- From our calculation, for [tex]\( b = 0.77 \)[/tex], the growth rate is [tex]\( -23\% \)[/tex]. This matches the statement.

### Conclusion:
Among the given statements, the correct one is:

D. If [tex]\( b = 0.77 \)[/tex], the weekly percent growth rate of the share's value is [tex]\( -23\% \)[/tex].

This matches both the provided base value and the calculated growth rate. Therefore, the correct statement is D.