Question

The least number of complete years in which a sum of money put outat 20% compound interest will be more than doubled is:

Answer 1

$\mathfrak{The\:Answer\:is}$

Let principal be P

P

(

1

+

R

100

)

T

>

2

P

P

(

1

+

20

100

)

T

>

2

P

(

1

+

20

100

)

T

>

2

(

120

100

)

T

>

2

1.2

T

>

2

Now let's find out the minimum value of T for which the above equation becomes true

If T = 1, 1.2T = 1.21 = 1.2

If T = 2, 1.2T = 1.22 ≈ 1.4

If T = 3, 1.2T = 1.23 ≈ 1.7

If T = 4, 1.2T = 1.24 ≈ 2.07 which is greater than 2

Hence T = 4

i.e., required number of years = 4

$\boxed{Hope\:This\:Helps}$