Question

A sum of money doubles itself in 10 years. In how many years it treble itself

Answer 1

Let the sum of money be x + y

So , it will be 2(x + y) in 10 years according to the question

Now , The doubled money will again be doubled in 10 years

So , Money raised in 1 year of the doubled money = 2(x + y) / 10

=> (x + y) / 5

Hence , in one year the money gets raised by (x + y) / 5

Now , Money raised in 5 years of the doubled money = Money raised in 1 year x 5

=> (x + y)/5 x 5

=> x + y

Now , from above We knew that (x + y) doubled itself in 10 years which gave 2(x + y) and then after 5 years , (x + y) amount of money got added in it .

So amount of money we have now = 2(x + y) + x + y

=> 3(x + y)

Hence it is triple of the original amount which was (x + y)

Hence the money got tripled in 15 years

Hope it helped you...

Answer 2

Answer:

In 20 years amount will be tripled.

Step-by-step explanation:

Let the Principal Amount, P = Rs. x

Given: Time period to get double , T = 10 years

Amount, A = Rs. 2x

We know that ,

Simple Interest, SI = A - P = 2x - x = x

Now, Using Simple Interest formula,

$SI=\frac{P\times R\times T}{100}$

$x=\frac{x\times R\times10}{100}$

R = 100/10 = 10 %

Now when

New Amount , A = Rs. 3x

From above Rate , R = 10 %

From Same formula, SI = 3x - x = 2x

This time we need To find Time in which Principal amount is tripled.

$SI=\frac{P\times R\times T}{100}$

$2x=\frac{x\times10\timesT}{100}$

T = 2 × 10

T = 20

Therefore, Amount is tripled in 20 years.