Help with q.9 and 10

[almostdonewithschooling]

Thank you

[jazzycab]

Thank you

For 9, use the compound interest formula:

Solve this in your CAS - note that the answer you get for \(n\) will be in years, so you'll need to convert to months.

For 10, the total amount repaid will be the amount of each repayment \(\times\) the number of payments made (i.e. \(500\times 36\)) and the total interest will be how much more that is than the $15000 that the loan was worth

[almostdonewithschooling]

Tried question 9 but didn't work

[jazzycab]

Tried question 9 but didn't work

What did you do, what answer did you get and what is the answer supposed to be?
I get 171 months (after 170 months, the investment hasn't quite doubled, but it has more than doubled after 171 months)

[almostdonewithschooling]

Got 14.20 as the yr and 170.4 as month but answer says 20 yrs

[jazzycab]

Got 14.20 as the yr and 170.4 as month but answer says 20 yrs

Certainly not 20 years, so something is incorrect in the answers (after 20 years, the account balance would be $13266.49)

[almostdonewithschooling]

True, oh well, thanks though

[MAGGOT]

Which exercise is this

[almostdonewithschooling]

This is 1/2 exercise  4c

[MAGGOT]

9) This question is asking how long will it take to reach to $10,000 using simple interest [i=prt formula]
i = final amount - initial amount  [you are trying to find out the interest only]
  = 10,000 - 5,000
p= 5,000
r= rate in months
 = (5.0/12/100)
t= the variable you are finding

Stick it all in into cas
   solve( 5000=5000*(5/12/100)*t,t)
   t= 240 months but the textbook didn't even read their own question and converted 240 months -> (divide by 12 months) into 20 years
or
rate (in months) * principal
= (5/12/100) * 5000
= 20.8333
then interest divided by 20.83
= 5000/20.83
=240 months

10)
a] total repaid = payment * time (in months)
                          = 500 * 3*12
                          = $18,000
b] interest = total repaid - principal
                 = 18,000 - 15,000
                 = $3,000

[jazzycab]

This is 1/2 exercise  4c

Ah, my bad, I completely missed the word 'simple' in the question - meaning this is definitely NOT compound interest.
The interest paid on this per year is \(\frac{5}{100}\times5000=\$250\).
The amount in the account will therefore increase by \(\$250\) every year.
We want to find how long it takes until it doubles (from \(\$5000\)), so therefore, we want the total interest paid to be \(\$5000\), which occurs after \(\frac{5000}{250}=20\) payments, or \(20\) years.

[almostdonewithschooling]

Thank you so much !