HELP PLEASE! The amount of interest earned by an account based on simple interest varies jointly as the principal amount and the number of years the .....

Question

.... investment has been held. If a principal of $6000 invested for 6 years earns $3240.00 in interest, how much would be drawn by $4000 invested for 11 years?

 

a. $2160.00

b. $3245.00

c. $3060.00

d. $3960.00

Answer 1

Hi Amanda, 

 

For this problem, where interest (I) varies jointly with principal (P), rate (R), and time (T), you'd use this equation: I=P•R•T to find R then plug that rate in to the 2nd problem, as follows:

3240=(6000)(R)(6)

3240=36000R then divide both sides by 36000 to get R =.09

 

I=(4000)(.09)(11)

I=$3960