Question

Find the simple interest

Answer 1

I=PRT
I=interest
P=principal=amount  you invested
R=rate in decimal, don't forget to convert percent to decimal
T=time in YEARS (don't forget, 12 months per year)

1. I=640*0.03*2=$38.4

2. I=1500*0.0425*4=$255

3. I=580*0.02*(6/12)=$5.80

5. I=1200*0.039*(8/12)=$31.2

6. I=290*0.125*(6/12)=$18.125

7. I=75*0.125*(1/12)=0.78125, in 1 month, in interest

8. 3000, 2 years,
 450=3000*2*r,
 450=6000*r,
 divide both sides by 6000
0.075=r
7.5%=rate

9.
a. 630=4200*r*3
630=12600*r
divide both sides by 12600
0.05=r
5%=rate

b. 5000 total
5000-4200=800
I=800
800=4200*r*4
800=16800*r
divide both sides by 16800
0.04761=r
4.761%=rate needed
6>4.7
yes