SOLUTION: Gasoline prices are rising at a rate of 0.8% per month. What is their approximate doubling time. (I think I got this part = 87.5 months?) By what factor will prices increase in 1 y

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: Gasoline prices are rising at a rate of 0.8% per month. What is their approximate doubling time. (I think I got this part = 87.5 months?) By what factor will prices increase in 1 y      Log On


   

Question 979123: Gasoline prices are rising at a rate of 0.8% per month. What is their approximate doubling time. (I think I got this part = 87.5 months?) By what factor will prices increase in 1 year? If gasoline costs $2.25 per gallon today, what will the price be in 8 years, assuming no change in the trend.
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
That seems good, depending on what source you use for natural logarithms.

y=p%2Ae%5E%280.008t%29
y, value for price after time t in months;
p, initial value when t is 0 months;

Finding time to double the price:
2=1%2Ae%5E%280.008t%29
ln%282%29=0.008t
t=ln%282%29%2F0.008
highlight%28t=86.64%29 but you might say 86.6 months.

Eight years is 8%2A12=96%2Amonths.
y after 96 months,
y=2.25%2Ae%5E%280.008%2A96%29
highlight%28y=4.85%29