Question

When Cat sold her car for $14,000, she put all of the money into a savings account. If the account earns 3.9% interest, how many YEARS will it take her to earn $1365 in interest?

Answer 1

Answer:

Roughly 7.35169 years

Step-by-step explanation:

So we want an increase of money of $1365

So our target value is 15,365

Let's model the expression: target = initial_value * (1.39)^y, where y is years

$15365 = 1365(1.39)^y$

This should immediately spark logarithms into your head

$11.25641 = 1.39^y$

$log_{1.39}11.25641 = y$

Use change of base formula:

$\frac{ln 11.25641}{ln 1.39} = y$

y = 7.35169 years