Deposit and Interest

Question

For a given interest rate, simple interest varies jointly as principal and time. If $2000 left in an account for 4 years earns interest of $320, how much interest would be earned in if you deposit $5000 for 7 years?

Answer 1

simple interest means no compounding at all

$40 per year per $1000

means 40(5)(7) = $1400 in interest

$5000 grows to $6400 in 7 years

$2000 grew to $2320 in 4 years

$1000 would grow to $1160 in 4 years

$1000 would grow to $1040 in 1 year

$40 per thousand per year in interest