if a painting is worth $135 and increasing by a factor of 1.2 every year for 70 years in the first year its worth $162 and in the second year its worth $194.40

1 answer

If a painting's value is increasing by a factor of 1.2 each year, we can represent its value in any year as follows:

\[ V(t) = V_0 \times r^t \]

Where:

  • \( V(t) \) is the value at year \( t \),
  • \( V_0 \) is the initial value (at year 0),
  • \( r \) is the growth factor (1.2 in this case),
  • \( t \) is the number of years since the start.

Given that the starting value \( V_0 = 135 \) and it grows by a factor of \( r = 1.2 \):

  1. At the end of the first year \( (t = 1) \): \[ V(1) = 135 \times 1.2^1 = 135 \times 1.2 = 162 \]

  2. At the end of the second year \( (t = 2) \): \[ V(2) = 135 \times 1.2^2 = 135 \times 1.44 = 194.40 \]

This matches your statement about the painting's value for the first two years, confirming the formula is correct.

To find the value of the painting after 70 years \( (t = 70) \): \[ V(70) = 135 \times 1.2^{70} \]

Using a calculator (or a computational tool) to find \( 1.2^{70} \):

\[ 1.2^{70} \approx 133.062 \]

Now calculate:

\[ V(70) \approx 135 \times 133.062 \approx 17,973.37 \]

So, the estimated worth of the painting after 70 years would be approximately $17,973.37.