Generic exponential growth model: y = Ao[1+r]^t
In this case: r = 3.5% = 0.035
y = 2Ao .....[the double of the initial value]
Then: 2Ao =Ao (1 + 0.035)^t
(1.035)^t =2
Take logarithm to both sides
t ln(1.035) = ln(2)
t = ln(2) / ln(1.035) = 0.693 / 0.0344 = 20.15
Answer: 20.15 hours.
Answer:
let the price of a pen be x
9 pens cost 7.20, so 9x costs 7.20. Therefore,
9x = 7.20
x = 0.8
Each pen is 0.8 dollars (80 cents).
