Question

Yuri invests $2,000 in an account with compound interest at 6%. Maria invests $3,500 in an account with compound interest at 4%. Using the rule of 72, how many years with it take Yuri and Maria to double their money?

a) Yuri’s money will double in approximately 18 years, and Maria’s money will double in approximately 12 years.
b) Yuri’s money will double in approximately 12 years, and Maria’s money will double in approximately 18 years.
c) Yuri’s money will double in approximately 20 years, and Maria’s money will double in approximately 25 years.
d) Yuri’s money will double in approximately 25 years, and Maria’s money will double in approximately 20 years.

Answer 1

b) Yuri’s money will double in approximately 12 years, and Maria’s money will double in approximately 18 years.

Step-by-step explanation:

Given that

Yuri invested amount = $2,000

Compound interest rate = 6%

Maria invested amount = $3,500

Compound interest rate = 4%

By using the rule of 72, the number of years for double their money is

For Yuri

= 72 ÷ 6%

= 12 years

For Maria

= 72 ÷ 4%

= 18 years

Answer 2

b) Yuri’s money will double in approximately 12 years, and Maria’s money will double in approximately 18 years.

Step-by-step explanation:

Given that

Yuri invested amount = $2,000

Compound interest rate = 6%

Maria invested amount = $3,500

Compound interest rate = 4%

By using the rule of 72, the number of years for double their money is

For Yuri

= 72 ÷ 6%

= 12 years

For Maria

= 72 ÷ 4%

= 18 years

Hence, b option is correct i.e Yuri doubles her money in 12 years while the Maria double its money in 18 years