If someone put $4000 in a savings account.At the end of 3 years,the account had earned$960 in simple interest.
At what annual simple intrest rate did the account grow explain?
How many more dollars would she have in the account if the intrest rate was 1% greater?

Question

If someone put $4000 in a savings account.At the end of 3 years,the account had earned$960 in simple interest.
At what annual simple intrest rate did the account grow explain?
How many more dollars would she have in the account if the intrest rate was 1% greater?

amistre64 · Answer

use the formula:

I = Prt, and solve for r

anonymous · Answer

I know the formula but I don't know how to use the formula to find r...

amistre64 · Answer

plug in whats given ... I is interest earned, P is starting principal, and t is time spent

amistre64 · Answer

960 = 4000(3)r ... how do we find r now?

anonymous · Answer

i dunno

anonymous · Answer

I'm really bad at math

amistre64 · Answer

you have to have some basic idea what to do ... im sure this question doesnt exist ina vaccuum.  any idea you have would be helpful to work from

anonymous · Answer

Divide maybe?

anonymous · Answer

I know how to do simple interest but not backwards

amistre64 · Answer

division is correct :)

so, we have 960 = 12000r,  dividing gets us:  r = 960/12000, and simplify as desired

amistre64 · Answer

then the question asks if the rate is  r + .01 since we need to convert 1% to a decimal form

anonymous · Answer

r=.08 so .08+.01=.09?

amistre64 · Answer

r = .08 is the first part, now use r=.09 to determine the interest for the second part :)

amistre64 · Answer

or rather:  r = 8% as is,  what if r was 9% how much interest would have been earned?

anonymous · Answer

okay so...$4000*.09*3?

amistre64 · Answer

yep

anonymous · Answer

Which would be...1080?

amistre64 · Answer

correct.  so the interest earned at 9% would have been 1080.  so the solution is either:  1080, or maybe the total in the acowingspan may be 4000+1080.  I cant really tell.

amistre64 · Answer

lol,  account ... typoed it into a bad word apparently

anonymous · Answer

Thankyou so much!! Sometimes I just need to be walked through the problem. :)

anonymous · Answer

It's k

amistre64 · Answer

critical thinking skills are acquired :) good luck

texaschic101 · Answer

I = PRT
P = 4000
R = R
T = 3
I = 960
now we sub
960 = 4000 * R * 3
960 = 12000R
960/12000 = R
.08 = R
8% = R

Now it is 8% for 3 years, so it grew at .08/3 = .0266 = 2.7% per year

If the interest was 1% greater...
I = PRT
P = 4000
R = 9% or .09
T = 3
now we sub
I = 4000 * .09 * 3
I = 1080

4000 + 1080 = 5080 would be in the account after 3 years at 9% interest