Question

Find the simple interest.
Principal: $400
Rate of interest: 12%
Time: 1 year

Answer 1

I = Prt Go!

Answer 2

so what do i do?

Answer 3

Substitution

P = Principle = $400.00
r = Simple Interest Rate = 12% = 0.12
t = 1 yr

Answer 4

so do i multiply it?

Answer 5

is it 576 ?

Answer 6

yes...I = P x R x T

Answer 7

way off...not 576
I = (400)(.12)(1)

Answer 8

48?

Answer 9

It is very unlikely that $400 would earn $576 in one year. You should ALWAYS have a reasonable magnitude in mind before you start.

I did it this way...
1) 10% isn't too far from 12%.
2) 10% of 400 is $40.
3) The answer should be a little over $40.

$48 is reasonable. $576 was not.

Answer 10

nicely done tkhunny :)