Answer:

the answer will. be 20 years.. by unitary method

Step-by-step explanation:

money doubles itself in 5 years

then in 1 times= 5/2

then the money will become 8 times in =5/2*8=20 years

Answer:

let sum=P

Time=2 Years

Amount=2P

According to the question

⇒P(1+ r/100)^5 =2P

⇒(1+ r/100)^5 =2

Cubing on both the side

⇒(1+ r/100)^15 = (2)^3

→ ( 1 + r/100)^15 = 8

⇒P(1+ r/100)^15 = 8P

Hence,in 15 Years amount to eight times itself