## jcdavi34 2 years ago Macy currently has a balance of \$3,418.82 in an account earning simple interest. Eighteen years ago she opened the account with an initial deposit of \$2,481. What is the interest rate on the account?

1. jcdavi34

is anyone there any members can help me please

2. jdoe0001

do you happen to have the Interest Rate Formula?

3. jcdavi34

no :(

4. jdoe0001

or, I should say, if you stick "X" amount in the bank today, and they say they'll give you 5percent interest, how much would you expect in 1year?

5. jdoe0001

would you expect X+[5percent of X]? after 1 year?

6. jdoe0001

ok, what's 10% of 100? :)

7. jcdavi34

10

8. jdoe0001

ok, so if you put \$100 in the bank, and they they'd give you 10 yearly interest, after 1 year, you'd expect \$100+[10% of \$100 = \$10], thus \$110 :)

9. jdoe0001

Macy originally put \$2481, after 18 years, with yearly interest, it became \$3,418.82 so \$3,418.82 = \$2481 + [\$2481 * RATE] *18years

10. jcdavi34

it ask for the interest rate

11. jcdavi34

7.7% 1.5% 5.6% 2.1%

12. Numb3r1

Even if it's earning simple interest, the interest will compound annually.

13. jdoe0001

\$\$ A= 3,418.82\\ P= 2,481\\ r = ? -------------\\ A=P+ Prt \implies P(1+rt)\\ A-P=Prt\implies \color{blue}{\cfrac{A-P}{Pt}=r} \$\$

14. jdoe0001

woops, ahemm

15. jcdavi34

7.7% 1.5% 5.6% 2.1% these are the answrs

16. jdoe0001

\$\$ A= 3,418.82\\ P= 2,481\\ \color{blue}{r = ?}\\ -------------\\ A=P+ Prt \implies P(1+rt)\\ A-P=Prt\implies \color{blue}{\cfrac{A-P}{Pt}=r} \$\$

17. jdoe0001

@jcdavi34 what does that give you?

18. jdoe0001

ohh,and T=18, 18years :/

19. jcdavi34

i got 2.1%

20. jdoe0001

\$\$ A= 3,418.82\\ P= 2,481\\ t=18\\ \color{blue}{r = ?}\\ -------------\\ A=P+ Prt \implies P(1+rt)\\ A-P=Prt\implies \color{blue}{\cfrac{A-P}{Pt}=r} \$\$ what do you get?

21. jdoe0001

2.1% that is :)

22. jcdavi34

thanks!