Question

HELP!
If the simple interest on $3000 for 6 years is $1620, then what is the rate?

Answer 1

I = PRT but we are looking for the rate, so let me change this formula to :
I/PT = R
I = 1620
P = 3000
T = 6
Now lets sub our stuff in the formula..
1620/(3000)(6) = R
1620/18,000 = R
.09 = R
now we will multiply .09 by 100 to make it a percent and we get 9%
9% = R

check...
I = PRT
1620 = (3000)(.09)(6)
1620 = 1620 (correct)

Answer 2

Perfect! Thank you!

Answer 3

did you understand what I did or do you have any questions ?

Answer 4

How did you know what formula to use?

Answer 5

Are there other formulas I need to know?

Answer 6

Simple interest formula is I = PRT. This formula can be rearranged if you are looking for something besides I.
It can be changed to :
I/PT = R
I/RT = P

Answer 7

Oh. OK! Thank you very much! That's helpful!

Answer 8

Glad I could help.....now this is not the formula for compound interest, just simple interest

Answer 9

Alrighty. Thanks!

Answer 10

anytime :)

Answer 11

Ok. Question for you. How do I find r
My teacher want me to use the formula for future value, A=P(1+rt) and elementary algebra to find the missing quantity. A=$1,920 ;P=$1,500 ;t= 4 years

Answer 12

A = P(1 + rt)
A = 1920
P = 1500
t = 4

now lets sub...
1920 = 1500(1 + 4r) -- distribute through the parenthesis
1920 = 1500 + 6000r -- subtract 1500 from both sides
1920 - 1500 = 6000r
420 = 6000r -- divide by 6000
420/6000 = r
.07 = r
If your teacher wants your r in a percent, multiply it by 100 and you get 7%

check...
1920 = 1500(1 + (.07)(4)
1920 = 1500 (1 + .28)
1920 = 1500 (1.28)
1920 = 1920 (correct)