Question

Rachel deposited $5,960.32 into a savings account with an interest rate of 4.2% compounded twice a year. About how long will it take for the account to be worth $9,000?

Answer 1

i'll give you the formula - try and calculate this value of t (time in years) yourself:
9000 = 5960.32 ( 1 + 0.042/2) ^ 2t
9000 = 5960.32* (1.021)^2t
1.021^2t = 9000 / 5960.32
2t * ln 1.021 = ln (9000/5960.32)
t = [ ln (9000/5960.32) / ln 1.021 ] / 2

Answer 2

i dont have a calculator :p

Answer 3

B = D ( 1 + r/n ) ^(nt)
9,000 = 5960.32 ( 1 + 4.2%/2) ^(2t)

1 + .042/2 = 1 + .021 = 1.021
9000/ 5960.32 = 1.51

-> 1.021^(2t) = 1.51
-> 2t ln 1.021 = ln 1.51
=> t = ln 1.51/ 2 ln 1.021 = 10 yrs

Answer 4

yes thats what i got 10 years

Answer 5

good job

Answer 6

Thanks you for your verification :)

Answer 7

yw