The most important thing here is converting the length into the same units. So:
3 feet 9 inches = 45 inches
now, we know that compound 'growth' can be worked out by multiplying the initial value by the decimal to the power of the years. So, relating to this question, the equation would be:
5 x α⁴ = 45
Now, we have to solve for α!
α⁴ = 45/5
α⁴ = 9
α = ⁴√9
α = 1.732050808
This is the increase every year written as a decimal so, if we want to work out the pure percentage, we have to subtract 1 and then multiply by 100:
1.732050808 - 1 = 0.732050808
0.732050808 x 100 = 73.20508076
Rounded to 2 decimal places the answer would be 73.21% !
